The invention provides a device and method for constructing an assembled crossing frame. The device and method are characterized in that the crossing frame comprises a tower base, a middle section and a tower head which are sequentially arranged in the vertical direction; the device comprises a jacking frame, a control device, a rope collecting and releasing mechanism and a power source; the rope collecting and releasing mechanism comprises two layers of stay wires which are symmetrically arranged on two sides of the tower head and two sides of the middle section respectively, and steering blocks and tension sensors are arranged between the stay wires and the rope collecting and releasing mechanism respectively; the jacking frame, the synchronous control device and the rope collecting and releasing mechanism are connected with the power source respectively. Compared with the prior art, the device and method for constructing the assembled crossing frame have the advantages that an inverted assembly mode is adopted, so that the quantity of aerial work is reduced, and safety is high; an assembly mode that the middle section is jacked hydraulically is adopted, so that tower assembly construction efficiency is high, and labor intensity of construction workers is relieved; it is guaranteed that the crossing frame is perpendicular to the horizontal plane all the time in an assembly process and after assembly is finished.