Three-time defending champion Wang Meng of China missed the Olympics after breaking her ankle last month. Li had little experience in the wild and woolly sprint, where getting off to a quick start is important. But she kept her cool while everyone else was falling around her.
"I feel very lucky," Li said through a translator.
She and one of her coaches cried tears of joy after China joined South Korea as the only countries to win the same short track event four Olympics in a row. The Koreans won the 3,000 relay in 1994, 1998, 2002 and 2006.
"I cried because I was so excited," Li said. "My coach told me this medal is for Wang Meng as well, so I felt very moved."
Li's victory made up for the surprising fall of teammate Fan Kexin in the semifinals.
Arianna Fontana of Italy took the silver and Park Seung-hi of South Korea earned the bronze.
Elise Christie of Britain caused the crash in the second turn of the opening lap when she veered into Fontana and sent both skaters spinning into the pads.
"I saw Elise come in and thought I'd stop her, but she kept going," Fontana said. "This is short track, so that's what happens. When I was falling I was so sad, then I saw the Korean girl fell and I thought I could still get something so I got up as quickly as I could. I got my silver medal, but for me it's gold."
Park got clipped and lost her balance going into the next turn. She fell into the sideboard, but got up and resumed skating. Li was closely trailing in last place when the chaos erupted. She took over the lead and went on to victory.
"I had more speed so I tried to stay out of reach of the fourth-place skater (Li)," Christie said. "I tried to pass and got bumped by the girl on the outside (Fontana)."
Park came across the line in last place, but Christie got disqualified, allowing Park to claim the bronze.
In the semis, Fan didn't even complete the first lap of the sprint, catching her left blade as she skated near the front. She crashed on all fours into the crew of workers who maintain the ice between races. They scrambled onto the top of the pads to avoid being injured by Fan's long, sharp blades.
Christie was lucky to be in the 500 final, surviving a photo finish to advance to the medal round after Fan's crash.
Park was trying to give South Korea a victory in the only short track event it has never won.
"It is such a great disappointment," Park said through a translator. "But it is also part of my destiny. I have to accept it."
It was a tough day at the rink for the South Koreans. The men's team had a call go against them in the 5,000 relay semifinals after a crash involving Lee Ho-suk and American Eddy Alvarez.
"The boys were not lucky," Park said. "I was not lucky either."
The referees advanced the U.S. team of Alvarez, J.R. Celski, Chris Creveling and Jordan Malone into the A final while the South Koreans were relegated to the B final.
Lee was leading on the outside late in the race with his left hand down on the ice when it clipped Alvarez's right skate. That sent Alvarez and Lee sliding into the pads.
"He slipped on his right and sat real deeply on his left, sticking his left arm out," Alvarez said. "It just so happened as I was crossing through, we collided. My hand and his skate. It didn't allow me to come through.
"I was going for the pass. I was coming with more speed. I'm glad the refs caught that."
There's a history of bad blood between the South Koreans and the U.S. dating to the 2002 Salt Lake City Games. They believed Apolo Anton Ohno stole the gold from Kim Dong-sung, who finished first in the 1,500 meters but was disqualified for blocking. The animosity toward Ohno grew so heated that the entire American short-track team withdrew from a World Cup event held in South Korea in 2003, citing death threats against Ohno.
But Sin Da-woon wasn't blaming the Americans after this latest tangle.
"We moved into them," he said. "It wasn't the Americans' fault. There was a mix-up in the signs. If we were clear with the signals then we could have avoided this. It's a pity we couldn't advance."
The U.S. waited anxiously while the referees sorted out the chaos.
"The moments between the fall and the call, there's a lot of doubt," Celski said. "Just disbelief that we didn't make it to the final. But our coach looked fairly confident."
Viktor Ahn led his adopted country of Russia into the relay final, which will feature five teams because of the U.S. getting in. The Netherlands, Kazakhstan and China also made the final.
In a surprise, Canada fell in its 5,000 semi and didn't make the final. The team of Michael Gilday, Charles and Francois Hamelin, and Olivier Jean had been a strong medal contender.
In the men's 1,000 heats, Ahn, 1,500 gold medalist Charles Hamelin of Canada and Celski of Federal Way, Wash., advanced to Thursday's quarterfinals.
Ahn led all the way in his heat, provoking the loudest cheers from the home fans. Ahn gave his adopted country its first short track medal when he earned a bronze Monday in the 1,500. Sin Da-woon of South Korea, which Ahn represented in the 2002 and 2006 Olympics, won a photo finish for second in the same heat.
Celski won his heat by a large margin.
Hamelin, the world's top-ranked skater in the event, is trying to become the third skater to sweep the 1,000 and 1,500 at the same Olympics.
Also advancing was Jean, Alvarez, Wu Dajing of China and Chris Creveling of Kintersville, Pa.