The invention discloses a steel wire rope pre-tightening device. The steel wire rope pre-tightening device comprises a steel wire rope winding system of a crane lifting mechanism, and a weight sensor.The steel wire rope pre-tightening device further comprises a pre-tightening winding drum, an auxiliary winding drum, a pre-tightening pulley, a guiding mechanism and a steel wire rope rigging; the pre-tightening winding drum is used for winding and keeping a to-be-pre-tightened steel wire rope; the auxiliary winding drum is used for winding the steel wire rope rigging; the middle of the pre-tightening pulley is provided with a pin shaft, and the two ends of the pin shaft are provided with a pre-tightening bracket; the free end of the steel wire rope rigging is fixedly connected with the pre-tightening bracket; the guiding mechanism comprises a chain block and a tackle; and the free end of the to-be-pre-tightened steel wire rope sequentially penetrates through the tackle and the pre-tightening pulley to be wound around the pre-tightening winding drum. According to the steel wire rope pre-tightening device, pre-tightening of the steel wire rope is conducted through the pre-tightening winding drum, the auxiliary winding drum, and the steel wire rope winding system of a floating crane, meanwhile, by monitoring the load of the weight sensor of the mechanism conducting pre-tightening,the effect that the pre-tightening force is within the set range is ensured, and the controllability and safety of the steel wire rope pre-tightening device are improved.