The invention discloses a preventive maintenance turnover mechanism which comprises a box, a screen assembly, four rod mechanism hinges, free positioning type slide supports and adjusting mechanisms. The screen assembly is hinged to the box through the four rod mechanism hinges, the free positioning type slide supports are arranged at two side edges of the screen assembly and used for supporting and positioning the screen assembly, and the adjusting mechanisms are arranged at two side edges of the box and used for achieving fine adjustment of the screen assembly. The four rod mechanism hinges are connected with the box and the screen assembly so that labor saving and smoothness during screen assembly turnover are guaranteed, the free positioning type slide supports support the screen assembly, the adjusting mechanisms perform fine adjustment to the preventive maintenance turnover mechanism so that reliability and stability of the preventive maintenance turnover mechanism are guaranteed, and simultaneously, the preventive maintenance turnover mechanism is simple in structure.