A Hydrostatic Energy Storage Transmission System(HESTS) designed for vehicle is presented in this paper*. A bench-scale HESTS was built in the Fluid Power and Control Laboratory of Harbin Institute of Technology. The laboratory testing HESTS was powered by a DC. motor which was controlled by a Silicon-Controlled Rectifier(SCR). Loads adding to the HESTS were regulated by a proportional valve control system.The HESTS is more complex because there are not only continuous variables-the shaft speed of the hydraulic axial piston variable displacement pump/motor unit and the position of the displacement-varying cylinder, but also discrete variables-the on/off states of clutch, 2/2 solenoid valve and 2/4 solenoid valve in the HESTS to be controlled. So a fuzzy logic controller with a mode selector is designed to perform the role of control to the HESTS. A personal computer stored control rules executes the tasks of data acquisition, fuzzy logic inference and control. Experimental results show that the HESTS had high efficiency and the control strategy was effective.