The 25-year-old defeated top seed Fabio Fognini of Italy 6-1, 3-6, 7-6 (9/7) in a thrilling three-setter in southwest China, where he was a qualifier.
Victory for Tomic -- his first ATP World Tour crown since Bogota in 2015 -- will propel the world-ranked 123 comfortably inside the top 100.
It was double disappointment for Fognini, who had been attempting to become the first Italian man to win four titles in a season.
For Tomic, it was a welcome change to be making headlines for the right reasons.
Once seen as a rising star, he has had a number of run-ins with authorities over the years.
In January he faced a backlash after boasting "I just count my millions" in response to failing to negotiate qualifying for the Australian Open.
In 2017, as his once-promising career nosedived, Tomic admitted he was sometimes "bored" during matches and not always giving 100 percent.