Swiatek beat the US Open champion 6-2, 6-3 to set up a clash with surprise package Liudmila Samsonova on Sunday.
The Pole seized the advantage early in the first set and never gave an error-plagued, seemingly injured Gauff a sniff of getting back into the match.
Swiatek wasted no time in gaining a double break of serve and wrapped up the opening set when the American slammed a forehand into the net.
The four-time Grand Slam winner broke again in the opening game of set two before the match was paused while Gauff received treatment for an apparent shoulder injury.
Afterwards, Swiatek picked up where she left off and sealed the win when the 19-year-old hit yet another forehand into the net.
"I feel like I'm playing less aggressively than past tournaments, and more solidly... I'm making less mistakes than I did before," Swiatek said at a news conference after the match.
"Playing against Coco is tough because she's really good at keeping the initiative, but she can also play great in defence," she said.
"You have to really be patient and ready for her to fight for everything... when I felt like the moment was right to push and play faster, I did."
Gauff had not lost a match since falling to compatriot Jessica Pegula in Montreal in August.
"I was feeling (the injury) in the first set," Gauff said after the match.
"It's definitely a new experience. I'm not used to playing with pain in general," she told reporters.
"When you're experiencing pain... your whole mind starts (thinking), 'Is it serious? Should I keep playing or not?'"
In the other semi-final, Samsonova upset world number five Elena Rybakina with a 7-6(7), 6-3 victory.
Rybakina had eliminated the top-ranked women's player and tournament favourite Aryna Sabalenka in straight sets on Friday.
But she stumbled against Samsonova, with the Russian - ranked 22nd - adding to a string of tournament scalps that includes two-time Grand Slam winner Petra Kvitova.
The China Open is taking place for the first time since 2019, after Beijing ended its isolationist zero-Covid policy.
The men's competition concluded on Wednesday, when Italy's Jannik Sinner beat world number three Daniil Medvedev in the final.
