The improvement of quality standard of automobile paint film and the application of effect pigments posed a higher challenge to the quality control of automobile body color difference. This paper discussed the causes of color difference of B pillar in the process of water-based IPⅡ topcoat，and analyzed the potential effects of equipment accuracy，body structure，and metallic coating characteristics. By studying the body structure and paint construction technology（manual and robot）， it was found that the design defects of the body structure led to the B pillar chromatic aberration，but the B pillar chromatic aberration was
effectively eliminated by optimizing the spraying trajectory and parameters of the robot，which provided reference and help for optimizing the body structure design and improving the chromatic aberration quality.