Abstract: For the load imbalance system of hoist based on frequency conversion control, Siemens PLC is adopted as the core of the elevator control system and the closed-loop vector control mode of Emerson CT SPM series inverter is adopted to realize wide range, high precision speed regulation and stable starting and stopping. It has the functions of rotating speed current double closed-loop vector control, power source filtering, energy consumption braking, high-speed counting, current detection, braking oil pressure constant, etc. The system equipped with semi-automatic, manual, maintenance and other operation modes, according to the process flow to achieve the lubrication pump, brake pump, solenoid valve and frequency converter of normal start and stop, to achieve speed control, load dynamic balance processing, reduce consumption and increase efficiency.