The invention provides a load power takeoff (PTO) device for a high-lift portal crane. The PTO device comprises a tension sensor and a stress release device for fixing a hoisting rope. The stress release device comprises a crossbeam, a thrust ball bearing, a rotating joint and a standard wire rope sling, wherein, the standard wire rope sling is fixedly connected below the rotating joint, the thrust ball bearing is arranged between the rotating joint and the crossbeam, the rotating joint is fixedly connected with the crossbeam in a free rotation manner, and two ends of the crossbeam are connected with the tension sensor through a pulling plate; and output of the tension sensor is connected to a main machine of a moment limiter in a cab of the crane. The load PTO device has the advantages that load measurement accuracy is improved and wear of the wire rope is reduced in the case of load hoistingzmeasurement; and a wire rope fixing device is equipped with the thrust ball bearing which can bear load and freely rotate so that errors in a PTO signal caused by the internal rotating force of the wire rope can be rapidly relieved by means of a stress release function, thus avoiding frequent operation of a protective device of the portal crane resulting from run-out tolerance of critical load weight.