A square steel cage guide assembly clamping fixture comprises a clamping fixture square pipe, a cage guide connection plate, a port positioning part, a side edge positioning part and a scribing caliper, wherein end cutting lines and edge milling lines are scribed on the two side surfaces and the upper surface of the clamping fixture square pipe; the cage guide connection plate is connected to the upper surface of the clamping fixture square pipe in a welded manner, and eyelets are formed on the cage guide connection plate; the port positioning part is connected to one end part of the clamping fixture square pipe in a welded manner; the side edge positioning part is connected to the lateral surface of the clamping fixture square pipe in a welded manner; the scribing caliper takes the shape of a door frame; the inner side width of the scribing caliper is no less than the side length of the clamping fixture square pipe; and the inner side height of the scribing caliper is greater than the side length of the clamping fixture square pipe. The clamping fixture has the advantages of simplicity in manufacture, low cost, high assembly efficiency and accuracy and high scribing efficiency, and saves the assembly field.