In order to optimize the integrated water and fertilizer fertigation machine and improve its fertigation performance, the working principle of Venturi injector was analyzed. According to the table of economic flow rate, the frictional loss and local loss of pipeline system as well as fertigation machine were taken into consideration. Taking flow of fertilizer absorption as evaluation index, single factor optimization experiment was carried out on some main parameters in Venturi injector which is the key component in the system by using CFD numerical calculation, including tapered angle α, divergent angle β and throat diameter d0. The influence rule of three parameters above on fertigation performance was obtained. Then through the orthogonal test with 3factors and 3levels, the combination of optimal structure parameters was got with CFD numerical calculation, that means, tapered angle α=20°, divergent angle β=8° and throat diameter d0=6mm. And the best fertigation performance was got when the angle between the absorption tube and the main pipe of Venturi was around 40°. Comparing with the simulated data and actual operation data of integrated water and fertilizer fertigation machine, it indicated that the fertigation absorption flow of Venturi was increased by about 38.6% after CFD numerical optimization, and the overall fertilizer absorption flow was increased by about 47.6% with fertigation machine matched with the fuzzy automatic control system. The energy saving effect is remarkable.