In order to improve shift quality of engineering vehicle transmission, research was carreied out on transmission electrohydraulic shift control system. Using AMESim software to construct a complete simulation model of the system, pressure requlation function was analyzed for main pressure system and clutch system. Regarded chargedischarge characteristics of shift clutch in shift process as a starting point, genetic algorithm was employed to optimize the main structural parameters of shifting clutches. The aim of improving quality of clutch shifting was arrived by improving the chargedischarge characteristics of shift clutch. Design and completed transmission shift hydraulic characteristics were carried out and validated. Results show that the hydraulic system can effectively improve the transmission shift clutch of chargedischarge characteristics, as well as improve the quality of shift, through hydraulic pressure regulation and optimization of structural paremeters of clutch. 