Using cold-rolled steel plate as the substrate,scanning electron microscopy(SEM)and X-ray fluorescence qualitative full scanning(XRF)were used to investigate the effect of cathodic electrophoresis forming chemical conversion films on the physical properties and neutral salt spray resistance of cold-rolled steel plate under different film pre-treatment processes.Using orthogonal experimental method to select the four factors that have the greatest impact on the reagent,analyze the primary and secondary factors that affect the film pre-treatment.The results showed that the film weight range of cold rolled steel sheet was 30~60 mg/m^(2),and the film thickness controlled by electrophoresis was 18~20μm.The primary and secondary factors affecting the physical properties of the film pretreatment and the neutral salt spray properties are pH,free fluorine concentration organic species temperature,the optimal scheme is pH 4.3,free fluorine 28 mg/L,organic 1,temperature 25℃.