Aiming at the problem that the transmission efficiency of construction vehicle hydraulic torque converter will decrease under the instantaneous high strength load, theoretical study on the automatic transmission of construction vehicle is conducted. A new shift schedule was deduced. According to the economical shift schedule, the efficiency of the torque converter can be restricted in an optimal range by the universal formula based on the diverse shift. Through the establishment of different control strategies for different phases of oil control curve for the shift course, to exert fully the function of adjusting the controller for oil pressure, the simulation results indicates that the method of fuzzy control adopted to control high speed on-off valve could adapt to the change of the system structure and adaptively adjust the control parameters. The tracking effect is very good, and it can achieve the aim of improving the shift quality. A satisfactory result was obtained through the test bench evaluation.