Abstract: In order to study the influence of impact line defects on the appearance quality of coating, a method of V-bending→flattening→stretching was proposed to simulate the generation of different degrees of impact line defects. The impact line depth, roughness, roughness profile coefficient, and waviness of boards with impact line defects were tested. The effect of impact lines on the appearance of long waves in coatings was evaluated using electrophoresis and high gloss tape. The results show that the depth of the impact line became shallower with increasing deformation, and the width of the impact line increased with increasing bending radius. The smaller the bending radius, the greater the changes in surface roughness, roughness profile coefficient and waviness of the board. As the deformation increased, the surface roughness and waviness of the board gradually decreased, while the roughness profile coefficient gradually increased. The correlation between the change trend and the material type and coating was weak. The larger the bending radius and deformation, the more advantageous it was to reduce the impact of the impact line on the appearance quality of the coating.