The invention provides a prestage model device of a deflection jet flow servo valve. The prestage model device of the deflection jet flow servo valve comprises an upper cover, a base, a left baffle and a right baffle. The upper cover covers the base in a sealed manner. A groove is formed in the center of the base. Multiple through holes are formed in the bottom face of the groove. The multiple through grooves are externally connected with pressure sensors. Each pressure sensor detects the pressure value of a corresponding measurement point. The left baffle and the right baffle are symmetrically arranged on the bottom face of the groove. Threaded holes formed in the bottom face of the groove are fixedly connected with countersinks formed in the left baffle and the right baffle. According to the prestage model device of the deflection jet flow servo valve, a prestage standard model of the deflection jet flow servo valve is amplified by certain times, the upper cover is made of polymethyl methacrylate and is transparent, so that flowing of prestage inner fluid of the deflection jet flow servo valve can be clearly observed, the pressure values of the pressure measuring holes at multiple positions can be more directly measured, and therefore effective motion state observation and pressure detection can be conducted on the prestage model of the deflection jet flow servo valve.