Qi landed solidly from his final jump, which included five full twists, to earn a score of 139.50 points and finish ahead of silver medallist Alex Bowen of the United States (121.27) and bronze medallist Maxim Gustik of Belarus (119.91).
Travis Gerrits, the only Canadian in the competition, finished 12th and last in the first round of the finals and did not qualify to move on.
Qi defended the title he won in 2013 in Norway. The world championships were not held in 2014, an Olympic year. Qi finished fourth at the Sochi Games.
Peel wins women's crown
Peel won the women's gold with a score of 88.47. American Kiley Mckinnon (88.12) took the silver, and defending champion Xu Mengtao of China (86.84) got the bronze.
Xu, the Olympic silver medallist, led the competition until landing on her back after the final jump.
"I just can't believe it," said Peel, who earned her sole World Cup win at the same venue in Austria three years ago. "[Xu] is an incredible jumper and her landing is usually bang on. I am just so happy to be on top of the podium."
Xu Sicun of China crashed after landing from her second jump and was carried off on a sled. There was no immediate update on her condition.
No Canadians were entered in the women's event.
Snowboard cross next
The world championships continue Friday with the men's and women's snowboard cross finals. Watch the action live on CBCSports.ca at 5:45 a.m. ET.