Goerges crumbled in the third, Barty claiming her first career win over the German 4-6 6-3 6-2.
Barty burst out of the blocks against Wang to take a 4-0 lead but, just as it looked like the opening set was over, the Chinese took advantage of some sloppy service games from her opponent to get back to 4-3.
But first, let me take a selfie: Ash Barty celebrates booking her place in the WTA Elite Trophy final.
The world number 22 looked calm and focused during the 73-minute semi-final, while Muguruza appeared out of sorts and frustrated, clattering her racket on to the court in the second set.
The 22-year-old Australian beat defending champion and top seed Julia Goerges in the semifinals and picked up where she left off in that match to win the US$2,349,363 tournament for the 12 best ranked players who fail to qualify for the WTA Finals. Barty consolidated her level in tennis and broke into the top 20 in the world.
Barty told WTA.com after sealing her third career title: "Thank you to all the fans".
"It's been a phenomenal year and I'm looking forward to a bit of holiday and then getting ready for the Australian summer".
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.
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.
Earlier, sixth seed Madison Keys pulled out of her semi-final tie against Garbine Muguruza with a knee injury. She's also a delight to watch in action, there's a wow factor in every single match I watch, practice too.