The invention discloses a device for monitoring opening and closing force performance of a fixed-cable hydraulic steel gate. The device comprises a support rod, a clamping force measuring pulley, a first fixed clamping pulley and a second fixed clamping pulley, wherein one end of the support rod is fixedly connected to a fixing member, the other end is fixedly connected to the clamping force measuring pulley, and the first fixed clamping pulley and the second fixed clamping pulley are respectively disposed on both sides of the clamping force measuring pulley; the support rod is further provided with a stress measuring sensor; the rope for lifting the gate sequentially bypasses the first fixed clamping pulley, the clamping force measuring pulley and the second fixed clamping pulley, and flexural deflection is produced at least by taking the clamping force measuring pulley as a fulcrum; the monitoring device further comprises an angle measuring device capable of measuring the flexural deflection angle formed by the rope at the clamping force measuring pulley, and the opening and closing force of the gate are calculated according to the flexural deflection angle of the rope and the axial pulling force received by the support rod. The device provided by the invention solves the problems such as big errors, slow response and dead zones of measurement of the opening and closing forceby the opening and closing force monitor.