By analyzing material characteristics,field production status and equipment process matching,it is found that electrophoretic lacquer with high titanium dioxide content is easy to appear electrophoretic lacquer block defect when stirring state is not ideal,and 95%of the defect occurs in the horizontal plane of the body.This defects can be improved and prevented by controlling the cleaning frequency of the UF chamber body and dripping plate,cleaning the swing rod contact,and controlling the tank fluid parameters.