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In order to optimize the matching of impeller with extra-thick blades and volute in centrifugal pump, the structure displacement and velocity of different volutes were simulated by two-way coupling fluid-structure interaction method. The numerical results showed that volute was influenced by alternately exciting force due to the flow field interaction between the impeller and the tongue, and vibration displacement and vibration velocity distribution changed cyclically at different time steps. The ratio of volute base circle diameter and impeller diameter D3/D2 had a significant impact on volute vibration. When D3/D2 was less than 1.013, the un-uniform velocity distribution induced by jet-wake in blade outlet leaded to the strong pressure pulsation and vibration of volute. However, the peak-to-peak value of the pressure pulsation was reduced and the vibration of the volute was weakened when the ratio D3/D2 gradually increased. In the design conditions, maximum vibration displacement in case A (D3/D2=1.013) was 4.288×10-6m, and the maximum vibration speed was 8.547×10-4m/s. In case C (D3/D2=1.19) was 2.923×10-6m and 5.253×10-4m/s respectively. The optimized case B (D3/D2=1.13) had the minimal vibration with the maximum displacement of 2.56×10-6m and the maximum vibration speed value of 4.823×10-4m/s. The results also demonstrated the direct relevance between the radial force law and volute vibration characteristics in centrifugal pump.