According to Kuan Tai Chen, most of the Shaw Brothers films took roughly two months to work on, but due to a tight schedule this had to be shot in one month. With this cramped schedule, director Cheh Chang was only able to direct during the night shoots, while uncredited director Hsueh Li Pao directed during the day shoots.
The famous final fight when Ma Yong Zhen takes on the hatchet gang took 10 days to complete.
The fight with the European challenger, played by Mario Milano, took roughly 5 days to complete.
Similar to when Bruce Lee starred in The Big Boss (1971), star Kuan Tai Chen was a Cantonese speaker, but this film was a Mandarin production. However, unlike Lee, who spoke Cantonese during shooting and was dubbed in Mandarin later on, Chen actually learned how to say his lines in Mandarin, even though he wasn't completely sure what they meant. Ironically, Pei-Shan Chang was the Mandarin voice actor for both Lee and Chen.
The late Chen Wo Fu was actually in the running to get the role of Ma Yong Zhen, but lost out to Chen Kuan Tai.