Through the simple analysis of the poor appearance of the waist line parts of each models in Dongfeng Honda automobile factory 1,the reasons affecting the appearance were explained from the aspects of substrate,coating,spraying parameters,etc,and relevant verification is carried out on the influencing factors such as the transformation of old painting equipment and new technology,In order to provide theoretical basis and reference for the appearance improvement of old line body,In order to provide theoretical basis and reference for the appearance improvement of old line body,the transformation of old equipment and the optimization of new process introduction.