CHENGDU, China — On the sixth floor of a down-on-its-luck shopping mall in this southwestern Chinese city, a brawny, hyperkinetic master of ceremonies going by the name “Train” strutted around a new fight ring, pumping up the crowd for a Friday night of punching, jabbing and kicking.

After a monthslong shutdown, “fight club” was back in business.

The funk music faded, lights brightened and two amateur boxers started squaring off. Yan Nan, a lithe 33-year-old office worker in a state-owned machinery company, was up against Li Guowei, a neatly muscular sports teacher, 4 inches shorter and seven years younger.

“I hope the kids in his class don’t mess up,” the master of ceremonies, whose real name is Wang Zijing, joked about Mr. Li to the hundreds of fans crowded around the ring.

The fight club in Chengdu, a city with about eight million urban residents and a reputation for spicy food and laid-back living, is a testament to entrepreneurial young Chinese trying something new, even when numerous obstacles, licenses and official jitters stand in the way.