Abstract: Based on the idiocratic immunoreaction between the mice immunoglobulin M(IgM) and rabbit anti-mice immunoglobulin G(IgG),the capillary electrophoresis-immunoassay was applied to the separation and testing of mice IgM and mice immunocompound. Factors influential to the separation of mice IgM,rabbit anti-mice IgG and mice immunocompound,including the concentration of buffer solution. pH values,time of sample introduction,and voltage of sample-introduction,were studied and optimized. Under the optimum conditions of 40 mmol·L-1 TAE and 1.0 mmol·L-1 EDTA (pH 8.5),12 s for time of sample-introduction and 18 kV for voltage of sample introduction,mice IgM,rabbit anti-mice IgG and mice immuno compounds formed in the immunoreaction were separated satisfactorily.