The invention relates to an overhauling line of a water supply and drainage system. The overhauling line of the water supply and drainage system comprises two overhauling lines, wherein one overhauling line comprises a to-be-overhauled buffer region, a water pumping device overhauling region, an electric drinking water boiler overhauling region and a storage region; the other overhauling line comprises a washing and drying region, a sewage box overhauling region, a toilet stool overhauling region and a storage region; the two overhauling lines share one to-be-overhauled buffer area; according to the requirements of an overhauling process of the water supply and drainage system, the convenience of overhauling and the sufficient utilization of space are simultaneously considered, so as to avoid repeatedly transporting devices, reduce repeated work and improve the overhauling efficiency; and the overhauling line is divided into the to-be-overhauled buffer region, a washing region, a working region and a repaired part storage region. Work station number for an overhauling test of the parts of the water supply and drainage system is small and the volumes of the parts are relatively large, so that an electric hoisting trolley is used for finishing the transportation of each part, ascending and descending a worktable and the like; corresponding equipment including the worktable, a test-bed, a control platform, a tool case and the like is arranged on each overhauling and assembling test region, thereby realizing the overhauling work of storing, decomposing, overhauling, assembling, testing and the like of the water supply and drainage system.