The invention relates to the technical field of building construction platforms, and discloses a liftable construction platform of an assembly type building and a construction method of the liftable construction platform. The liftable construction platform comprises a working platform horizontally surrounding the periphery of the building, masts used for supporting the working platform, a bridge crane located on the working platform, a concrete spreader installed on the bridge crane, and a net rack located at the top end of the working platform. The working platform is formed by splicing standard joint trusses. The working platform comprises an upper platform body, a lower platform body, truss columns and a climbing system, wherein the upper platform body and the lower platform body are arranged in the mast direction in parallel in a spaced mode; the truss columns are connected with the upper platform body and the lower platform body; and the climbing system is arranged in the truss columns. The side length of the cross section of each truss column is larger than the corresponding side length of the cross section of each mast. Each mast is sleeved with the corresponding truss column. Each mast is formed by splicing standard mast joints. The bridge crane is arranged between two long beams of the upper platform body in a crossing mode. According to the liftable construction platform and the construction method, hoisting equipment is combined with the construction platform, prefabricated members can be arranged in place easily, the position accuracy is high, and the installation efficiency is high.