Russia's Ilya Zakharov had dominated the early qualifiers, leading He by 6.75 points.
However, the Chinese competitor scored a total of 510.15 from his six dives in the semis, pushing the Russian back into second place by a margin of 4.55.
After claiming the opening five Diving events, China is targeting a clean sweep of all eight golds in London after finishing with seven from eight in Beijing.
He scored 91.80 for his inward 3.5 somersault and followed it up with 91.20 in his forward 4.5 somersault, which lifted him to first place.
He said afterwards: 'The gold is in my mind right now. I hope I can continue to do well.
'I don't know about other records we will be creating. My job is to dive well and that's all. The rest follows. There is some tough competition so I have got to focus.'
I will try harder. It is not easy with China doing so well.Ilya Zakharov
Zakharov fell to ninth midway through the round before rallying to finish second at 505.60.
The Russian said: 'I will try harder. It is not easy with China doing so well.'
He's team-mate, Qin Kai, who won the Synchronised 3m Springboard gold with Luo Yutong, finished third with 500.35.
The finals will take place in the evening session.