Aimed at the requirements of conveying and lifting heavy module vertically and horizontally of nuclear power plant, the hydraulic system of module lifting vehicle and level regulating are developed. The key problem was solved of the hydraulic loop design when the lifting over the center of mass and cylinder under the negative load. Firstly, the two steps lifting scheme were adopted to improve the system stability. Then, the back outriggers and cylinders with machinery locking were chosen to avoid higher pressure of the hydraulic system when the module was lifted to the state of lifting over the center of mass, which eliminated hidden safety danger of broken pipes caused by the high pressure. At the same time, the lifting angle was detected and fed back to the control system to adjust the flow output of propotional flow valve so as ensure consistency of stretch out speed in the whole journey of multi-stage cylinder at lifting. Through actural test verification of the system, the using results are shown good that the whole lifting process of the module has very strong robust and stability.