The 22-year-old Australian beat defending champion and top seed Julia Goerges in the semi-finals and picked up where she left off in that match to win the $2,349,363 tournament for the 12 best ranked players who fail to qualify for the WTA Finals.
It was Barty's third WTA title after her triumphs on grass at the Nottingham Open earlier this year and at the 2017 Malaysian Open but by far her biggest.
"It's been a great finish in China this week," she said. "It's been a phenomenal year and I'm looking forward to a bit of holiday and then getting ready for the Australian summer."
Barty, who reached the semi-finals of the Wuhan Open in her last singles tournament, romped to a 4-0 lead over Wang in the first set at the Hengqin Tennis Centre.
Wang, who has risen to 22nd in the world on the back of a fine run of form, staged a minor comeback to get back on serve at 4-3 but a delightful drop shot handed Barty her third break and she served out to win the set.
Barty, who took a break from tennis earlier in her career to play cricket, has proved almost unbeatable when she has won the first set this year as she has solidified her position in the world top 20.
While her service was clicking, Barty's all-court game did the rest and after being forced to save a break point for 2-2, she broke Wang again to go 4-3 up.
From then on victory never looked in doubt.
As Barty attacked, China's number one was struggling to hold onto her own serve let alone mount a counter-attack, and the Australian sealed the victory with a perfectly executed backhand crosscourt volley.
Wang, 26, earned her place in the final by beating Garbine Muguruza on Saturday, having been drafted in to play the semi-final after Madison Keys withdrew with a knee injury.
