The role of the Little (Young) Soldier was originally written for Jackie Chan, who came up with the idea of the story Little Big Soldier 20 years ago. However, it took 20 years to wrap up the script, and now Jackie Chan is cast as the Big (elder) Soldier instead. Leehom Wang takes the role of Little (young) Soldier.
When he could not take the role of the young general, Jackie Chan originally considered Daniel Wu to play the part of the young general, but Chan disregarded the thought after realizing that he had already filmed two movies earlier with Wu. Chan's wife, Joan Lin, suggested their son Jaycee Chan, but Chan objected to it. Lin later suggested Leehom Wang, whom Chan agreed to immediately.