On was born on 11 May 1977, in Providence, Rhode Island. He was approached by China Star founder Charles Heung and filmmaker Tsui Hark to take over the role of one of Jet Li's film characters, Black Mask, in Black Mask 2: City of Masks (2002).

On won a Hong Kong Film Award for Best New Actor Award for his role in Siu nin a Fu (2003) (Star Runner). He shared the screen with the man who influenced him, Jackie Chan, in New Police Story. On is slated to star in two action films in 2010, True Legend and Bad Blood.

Aside from his filmmaking career, On is also a singer. He has released some tracks, including a duet with Jolin Tsai called "Angel of Mine" and others. On's hobbies are martial arts and video games. On is currently training in Wing Chun Kung Fu with good friend, actor and martial artist Philip Ng, and has studied Thai boxing under former world kickboxing champion and actor Billy Chau in preparing for Star Runner. On has trained in wushu at the Shaolin Temple and studied film fighting under former Jackie Chan Stunt Team leader Nicky Li for his first film, Looking for Mr. Perfect, which was shot before Black Mask 2: City of Masks but released in 2003.