Wong Fei-hung was a famous practitioner of hung gar kung fu, although the techniques Jet Li uses are mostly of the long fist method and tai chi.
Jet Li's voice was dubbed in post-production for the Cantonese-language version because he is not a Cantonese speaker (he spoke in Mandarin entirely during filming).
Jet Li badly damaged his knee when Wong Fei Hung jumps out of the tea shop using his umbrella. For this reason a lot of the final fight was performed while Li was in plaster, meaning he had to be doubled for some of the moves. A lot of the shots are from the waist and above, to hide his plaster.
According to the commentary on the Region 1 DVD, this movie started out as a proposed new film to star Jackie Chan, Sammo Kam-Bo Hung, and Biao Yuen. Jackie would have played Wong, (which he'd previously played in Drunken Master (1978)), Sammo would have played Butcher Wing (as he did in The Magnificent Butcher (1979)), and Yuen would be Leung Foon. This idea fell through, with only Yuen Biao making it into the finished film.