Australia's world number one will meet Caroline Wozniacki or Naomi Osaka on Sunday after surviving three tense sets against Kiki Bertens.
Barty committed 52 unforced errors but still just about emerged victorious in a nervy 6-3, 3-6, 7-6 (9/7) triumph in Beijing.
The 23-year-old, who won the French Open and surged to the top of the rankings in June, said there had been "massive growth" in her mental fortitude when she faces crunch points.
"That's gone hand-in-hand with adding some new people to my team, trying to work with them behind the scenes," Barty, who five years ago took a break from tennis and played cricket, said. "Not just for my tennis — it's for my life, my health and wellbeing, as well, which has been the best thing. I have never been happier off the court, never been happier on the court. It's been a brilliant time in my life."
Barty looked all set to rush into Sunday's final and dominated the first set against the shell-shocked Bertens, eighth in the world.
But the 27-year-old Dutchwoman struck back to win the second set of their semi-final by the same 6-3 scoreline and take the match to a decider.
They went with serve until the fifth game of the third set, when Bertens profited from another Barty error to go a break up.
Barty was on the ropes. Bertens though lost her nerve when serving for the match, the momentum swinging back in the Australian's favour.
Barty went down 3-0 in the tiebreak, but demonstrated her newfound resilience to overcome the deficit and a match point to seal victory.
Title-holder Wozniacki and reigning Australian Open champion Osaka play their semi-final later Saturday.
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