Abstract: The oil-line structure, control system and their working principles of the hydraulic lifting system for the main magnets of CYCIAE-30 cyclotron are introduced. The application of six years proves that the specification of the system matches the requirements: the oil cylinder maximum stroke of 850 mm,the eight slot positioning dowels repositioning accuracy of ±0. 01 mm, the two oil cylinders moving in step accuracy of 5-10 mm. The system is safe, reliable and easy to be operated.