"The Demon" entered the match seeking to atone for an 0-10 record against the world No.2, but while he fought back after dropping the first set, the Australian ultimately lost 6-3 4-6 6-2.
Sinner will play his third straight China Open final - having won the event in 2023 - against American 19-year-old Learner Tien.
Tien advanced when former US Open champion Daniil Medvedev retired injured from their semi-final, with Tien leading 5-7 7-5 4-0.
Making a typically fast start in his bid to maintain his dominance of de Minaur, Sinner broke the world number eight to love for a 4-2 lead, but he had to battle hard in the next game to hold serve.
Sinner comfortably wrapped up the first set from there but ran into trouble early in the second, appearing to struggle physically at times, before tight holds helped him go level at 3-3 and then 4-4.
Third seed de Minaur persevered to win only his second ever set against the four time Grand Slam winner with a gutsy performance in the 10th game.
But Sinner regrouped in the decider, breaking in the first game and holding off his opponent to reach a ninth straight final on hardcourts.
"I felt like the level was very high," Sinner said. "Many great rallies, many great chances for both."
World No.52 Tien will be playing his first tour final as a heavy underdog against Sinner.
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