She was able to bounce back though with a 6-3, 6-4 win over Caroline Garcia before defeating defending champion Julia Goerges 4-6, 6-3, 6-2 in the semifinals.
"I know that whenever I have played (Wang) in the past, it's always been an extremely tough match", said Barty.
While Barty flourished, Wang sprayed the ball wide and long all too often and, although she got back into the set, nothing was going to stop her opponent moving ahead.
Barty, who took a break from tennis earlier in her career to play cricket, has proved nearly unbeatable when she has won the first set this year as she has solidified her position in the world top 20.More news: Oprah doorknocks in support of possible first black female United States governor
Her victory makes her the first Chinese player to reach the final in Zhuhai, with the previous best result being Zhang Shuai's semifinal showing in 2016.
"It's been a truly phenomenal year", said the 22-year-old, who also made the WTA finals for doubles in Singapore last month. Barty consolidated her level in tennis and broke into the top 20 in the world. "It's been a great finish in China this week", she said. "I'm very excited that it's finished now, time for some vacation and "relax" time before we gear up for the Australian summer".
Wang replaced Madison Keys at the eleventh hour, after the American who won the Azalea Group was forced to withdraw due to a left knee injury.
The final 11 games of the match went the way of Wang, who needed only 24 minutes to bagel Muguruza in the second set as the two-time grand slam champion's season ended in disappointing fashion.
As Barty attacked, China's No. 1 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.