The Queenslander defeated Caroline Garcia in her second match; the Frenchwoman then going on to beat Sabalenka in their clash to allow Barty to sneak into the semi-finals.
She needed to come from a set down to oust defending champion Julia Goerges in the last four, and her reward was a comfortable outing on Sunday.
"I know that whenever I have played Q in the past, it's always been an extremely tough match", Barty told WTA Media.
Wang struck the first blow in an 11-minute Muguruza service game, taking her third break point, and the Spaniard was unable to recover from that setback.
But first, let me take a selfie: Ash Barty celebrates booking her place in the WTA Elite Trophy final. Barty consolidated her level in tennis and broke into the top 20 in the world. "I'm very excited that it's finished now, time for some vacation and "relax" time before we gear up for the Australian summer".
The 22-year-old, accomplished the titles on grass at the Nottingham Open earlier this year and at 2017 Malaysian Open but by far her biggest.
Barty had her share of luck to even make the tournament decider after losing her opening-round robin-match in straight sets to Aryna Sabalenka.
"It's been a great finish in China this week", Barty said after Sunday's win.
"It has been a phenomenal year, it really has".
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 second set was more evenly contested with just one break of serve in 10 games with a flurry of errors from Wang leading to the sole break in the seventh game. Wang trails Barty 0-1 in the pair's head-to-head record after falling in straight sets against the Australian in Strasbourg earlier this year.