The structure diagram and working principle of the direct actuated overflow valve were given, the flow continuity equation and the dynamic force balance equation of the valve core were established. The dynamic simulation model was established with the AMESim software based on the mathematical model. The influence law of the structural parameters on its dynamic performance was systematically studied. The simulation shows that overshoot is increased slightly and the stable time of dynamic pressure is lengthen with spool quality increased; the spring stiffness increases, the overshoot decreases, the stability pressure increases, and the spool displacement changes little; the valve core damping increases, the pressure overshoot increases and the stability time lengthen; the seat diameter reduces, the pressure overshoot reduces, the stable pressure increment is larger, and the spool displacement increases; the seat diameter reduces, the pressure overshoot reduces, the stability pressure and spool displacement increases; with the increase of step flow, the pressure overshoot and the stability pressure increase.