Shang, 19, defeated the Wimbledon semi-finalist from Italy 7-6 (7/4), 6-1 to thrill the home crowd and join Wu Yibing as the only winners on the ATP Tour from China.
Wu triumphed at Dallas last year.
Shang's victory over the top seed and Paris Olympics bronze medalist makes him the first player born in 2005 or later to win an ATP Tour title.
"I'm really delighted to have lifted the trophy here in front of my home crowd," said Shang, who is ranked 55 in the world.
"While I felt some pressure to perform, the crowd really encouraged and supported me to play my best tennis throughout the week.
"It's been amazing."
There was to be no repeat for China however in the Hangzhou Open final, where home hope Zhang Zhizhen went down 7-6 (7/5), 7-6 (7/5) to Croatia's Marin Cilic.
It was Cilic's first ATP Tour triumph since 2021.