The invention relates to a crane frequency conversion control system and a crane frequency conversion control method. The crane frequency conversion control system comprises a hydraulic system and anelectric control system, wherein the hydraulic system comprises a PLC automatic control system, a luffing system, a main lifting system, an auxiliary main lifting system, a rotation system, a main motor, a main pump and a hydraulic oil tank, the PLC automatic control system controls a hydraulic control proportional multi-way valve through an electric proportional pressure reducing valve group, anddetects the rotation speeds of a main lifting winch, an auxiliary main lifting winch, a luffing winch and a rotation mechanism respectively through an encoder, the electronic control system comprisesa control box, a left switch box panel, a right switch box panel, a cab transition wiring box, a hydraulic oil tank wiring box, a suspending arm transition wiring box and a torque meter main chassis,and the control box controls a left lock motor and a left cable stabilizing motor through a second frequency converter, and controls a right lock motor and a right cable stabilizing motor through a third frequency converter.