Abstract: In order to study the effect of blade wear on the hydraulic performance , internal flow characteristics of important plant water pumps, CFD software is applied to perform constant and non-constant calculations on essential service water pumps based on the standard k-ε turbulence model. The hydraulic performance, internal flow characteristics and pressure fluctuation of volute flow channel under different blade wear were analyzed. The results show that the blade wear will increase the turbulent kinetic energy in the impeller channel and generate a low pressure region locally. With the increase of wear degree, the low pressure zone gradually diffuses into the impeller flow channel and finally reaches all the flow channels, which makes the flow field of important factory pumps unstable, the head and efficiency decrease, and the head and efficiency at 5/20 wear are 1.2 % lower than those without wear. With the increase of wear degree, the waveform of pressure pulsation becomes disordered, the amplitude of axial frequency is second only to the main frequency, and it is higher and higher, and it begins to dominate. In the frequency domain diagram, the peak value increases with the increase of wear degree, indicating that the blade wear makes the flow in the pump unstable and the fluctuation intensifies.