The invention relates to a turnover mechanism for installing the external coating of the side wall of a motorcar, comprising a base plate, a first main body supporting seat, a second main body supporting seat, a first turnover bearing, a second turnover bearing, a first low limited post, a second low limited post, a first high limited post, a second high limited post, a first air cylinder seat, asecond air cylinder seat, a first air cylinder and a second air cylinder, wherein the first main body supporting seat and the second main body supporting seat are arranged on the base plate, the first turnover bearing and the second turnover bearing are respectively arranged on the left sides of the first main body supporting seat and the second main body supporting seat, the first low limited post and the second low limited post are respectively arranged on the right sides of the tops of the first main body supporting seat and the second main body supporting seat, the first high limited postand the second high limited post are respectively arranged on the base plate and are positioned on the left sides of the first main body supporting seat and the second main body supporting seat, and the first air cylinder seat and the second air cylinder seat are respectively arranged on the base plate. The turnover mechanism is characterized in that the front part and the rear part of a turnoverbody are respectively connected with the first turnover bearing and the second turnover bearing; and the first air cylinder and the second air cylinder are connected with the turnover body. The turnover mechanism has the advantages that single-side manual external coating installation is realized, the safety is ensured, the quality of external coating installation is improved, and the requirementof the production line rhythm is satisfied.