The invention relates to a tool special for maintenance, in particular to an auxiliary installation tool of a gas relay (a flow control valve). By the auxiliary installation tool, the problem of difficulty in installation during replacement of the gas relay at present is solved. The device comprises a corrugated pipe compression device and a gas relay support device, the corrugated pipe compression device comprises two telescopic rods, a clamping tail clip is arranged at one end of each telescopic rod so that the telescopic rod can be fixed at two sides of a flange, screw rods are arranged at the other ends of the telescopic rods, the telescopic rods are connected with a strip-shaped compression plate by nuts, transverse position-adjustable installation holes are formed in two ends of the strip-shaped compression plate, an effect of compressing a corrugated pipe can be achieved by fastening nuts at opposite sides, two special support gaskets are configured and are used during disassembly of a compression device, the gas relay support device comprises two horseshoe support racks and a rectangular groove-shaped support plate, screw rods are arranged at two ends of the support racks, longitudinal position-adjustable installation holes are formed in four corners of the rectangular groove-shaped support plate, the rectangular groove-shaped support plate is used for placing the gas relay needed to be installed, the two support racks are connected with the rectangular groove-shaped support plate by nuts, and the height of the support plate is adjusted by adjusting nuts at the bottom.