After a slight bobble in the morning preliminaries led to a third-place showing, Chen took control in the afternoon with 373.65 points over her five dives.
Tonia Couch of Britain was next with 368.15 points, followed by Si Yajie of China with 341.85. Si was on top after the preliminaries but couldn't hold off Chen in the semifinals.
Roseline Filion of Laval, Que., qualified fourth with 327.45 after finishing 13th in the preliminary round.
"The hardest part of the competition is now done," said Filion, 26, a silver medallist earlier this week on 10-metre synchro with Meaghan Benfeito. "A day with prelims and semis takes a lot of energy especially on a hot day like today and 36 divers in the competition. I was glad I was able to relax properly between the prelims and semis to refocus."
The top 12 advance to Thursday's final. They include Pandelela Pamg of Malaysia, last year's Olympic bronze medallist on the tower, and Victoria Lamp of the United States. But the silver medallist in London, Brittany Broben of Australia, was eliminated.
China has won five of the first six diving events in Barcelona.