The invention relates to a modular construction method of a large-span, super-wide and super-heavy truss. The construction method comprises the following steps that structural modeling analysis is conducted on the truss through modeling software, and factory modules of the truss and the positions and structural forms of temporary reinforcing structures of the factory modules are determined; the truss is assembled and manufactured, and the temporary reinforcing structures are mounted; the truss is divided into the multiple modules according to models, according to the transport requirement, for a single piece during dividing, the largest width is smaller than or equal to 8.5 m, the length is smaller than or equal to 26 m, the weight is smaller than or equal to 60 t, and then the modules are transported to a construction site in batches; construction preparation is conducted before truss mounting; the modules are assembled into the whole truss; the temporary reinforcing structures are dismantled; and the truss is overall hoisted in place. The modular construction method has the characteristics that construction is convenient and rapid, safety and reliability are achieved, the cost is reduced, and the construction period is shortened.