Abstract: Abstract: In order to improve the sewage pump performance, the high-head sewage pump with the specific speed of 60 was investigated in this paper based on the methods of numerical simulation, particle image velocimetry (PIV) measurement and performance test. Matching of high-head sewage pump impeller with extra-thick blades and three volutes with different base circle diameters was optimized. Steady numerical results show that the volute base circle diameter D3 has greater impact on the hydraulic efficiency of the impeller with extra-thick blades. The base circle diameter of volute has smaller impact on the efficiency and head when the ratio D3/D2 of the base circle diameter of volute and impeller diameter is less than 1.13, while the efficiency decreased by about 3.3% when the ratio D3/D2 increased to 1.19 because of the increasing circulation losses in the volute. Unsteady simulation of impeller and volute coupling flow field show that extra-thick blade and volute matching will directly affect the flow field in pump, and the peak-to-peak value of pressure pulsation and unsteady radial force the of case A (D3/D2=1.01) is about three times that in case B (D3/D2=1.13), while the reduction of the peak-to-peak amplitude is very small when the ratio is greater than 1.13. The test results show that case B (D3/D2=1.13) has good performance and steady flow field with a steep drop curve of Q-H and saturated shaft power. The maximum value of shaft power is less than 45 kW compared with the national standard 55 kW, so the cost of production will be reduced. The efficiency of case B in design condition is 71.80% which is 10.8% higher than the national standard, and its amplitude of pressure pulsation and unsteady radial force are small. Three channels in impeller are formed by three extra-thick blades, so the maximum solid particle diameter of 40 mm could pass from it. PIV experimental results show that the flow field in the impeller is stable in a large range of flow rate without flow separation and backflow.