This study aims to investigate the effects of rice husk biochar (RB) and maize stalk biochar (MB) on the distribution of copper (Cu) in soil, Cu accumulation in pak choi, and plant growth. Pot experiments were conducted using Cu concentrations (0, 50, and 200 mg/kg soil) and biochar proportions (0%, 1%, 2%, and 3% w/w). Pak choi shoots and roots were determined by dry weight, analyzed for Cu concentrations in plants, and the distribution of Cu fractions in the soil. The results indicate that medium biochar proportion (2%) is most effective in reducing Cu concentration in plants and improving the growth of pak choi. RB biochar is found to play a more significant role than MB biochar in Cu-contaminated soil (200 mg/kg). In non-contaminated Cu soil (50 mg/kg), a low biochar proportion (1%) is most suitable for improving the growth of pak choi, with MB biochar being more effective than RB biochar. Strong correlations were observed between mobile Cu fraction proportion and Cu concentrations in plants, indicating that they can all be used to predict Cu bioavailability in soil. This study provides valuable insights into the use of biochar to reduce Cu accumulation in pak choi and selecting appropriate biochar types.