Numerical simulation of the jet flow field with different orifice parameters of deflector jet valve by using CFD software was carried out. The jet velocity and pressure distribution characteristics of deflector jet valve and the influence law of different orifice parameters D1, L1, D2, L2 on jet velocity and pressure were obtained. It is found that the maximum value of the jet velocity from the nozzle is gradually decreased and then increased to the 08 mm position after the nozzle jet velocity; The jet pressure increases at first and then decreases to a smaller value at the 08 mm position, finally, the maximum value is reached at the valve body of two receiving port. The D1 plays a decisive role in jet flow of the V type diversion port, jet pressure and recovery pressure difference. The upward shift of jet velocity curve and the downward shift of jet pressure curve when increasing D2. The L1 has effect on the jet pressure, however the influence of L2 on the jet field can be neglected. The research results can provide reference for the engineering design and optimization of high performance deflector jet servo valve.