Based on the k-ε (k is turbulent kinetic energy, ε is turbulence dissipation rate) turbulence model, this paper uses the inlet mass flow rate and outlet static pressure as numerical calculation conditions to establish a numerical simulation model of the internal flow field of the diaphragm valve. The accuracy was experimentally verified. On this basis, the model was used to analyze the internal flow characteristics and pressure field distribution of the valve body under different inlet flow conditions (2.787kg/s to 33.273kg/s), and the precise quantities of the inlet flow rate and valve body head loss were established. relation. The results show that: 1) Numerical simulation can better predict the head loss of the valve body under different flow conditions. When the inlet flow rate is 5.546kg/s, 11.091kg/s and 16.637kg/s respectively, the relative error between the test and numerical simulation is only are -6.433%, 4.619% and 7.264%. 2) Under the condition of constant inlet flow, from the inlet to the outlet, the static pressure in the flow channel generally shows a decreasing trend. Inside the valve body, the flow channel shrinks due to the obstruction of the valve sill and the flow hits the diaphragm to cause deflection. Large static pressure gradient. 3) After the water flow passes through the narrow channel on the valve sill, an obvious cavitation zone is formed downstream of the valve body, accompanied by a certain backflow phenomenon. The cavitation zone downstream of the valve body mainly appears in the 1/3 fluid domain from the outlet. , as the inlet flow increases, the vortex downstream of the valve body becomes more intense and the backflow phenomenon becomes more significant, but the scope of the backflow area does not increase significantly. 4) Based on the accuracy verification of the model, the model was used to further analyze the internal flow characteristics and pressure field distribution of the valve body under 18 inlet flow conditions, and establish the quantitative relationship between the inlet mass flow rate Q and the valve body head loss △P , when the inlet mass flow Q is from 2.787kg/s to 15.428kg/s and the Reynolds number is from 37927 to 215984, the fitting equation is △P=2076.31Q-7567.49, R2=0.964; the inlet mass flow is from 17.141kg/s to 33.273kg/s, the fitting equation when the Reynolds number is from 240097 to 467009 is △P=5688.02Q-67317.39, R2=0.993, which provides a reference basis for the hydraulic calculation of the irrigation pipe network.