Double suction centrifugal pumps are widely used in pump stations along the Yellow River. The impeller is the important part and its erosion problem is common. Impeller is a high speed rotating part, there is rotor-stator interference resulting in the erosion characteristics of the impeller is unsteady. The Euler-Euler method was applied to simulate the unsteady solid-liquid two-phase flow in a double suction centrifugal pump. The unsteady characteristics of the erosion rate, impact angle, solid concentration and solid velocity on the impeller wall under different working conditions were analyzed. The results showed that the erosion rate, impact angle, solid concentration and solid velocity of the impeller surface were periodic, which were equal to the impeller rotation period. The erosion rate of steady calculation was far less than the results of unsteady calculation. The steady calculation cannot predict the erosion rate accurately. The most erosion parts were the blade head and blade tail. The erosion area in the middle of the suction surface was larger than that in the pressure surface, while the erosion area of the pressure was larger than that of the suction surface at the blade head and blade tail. The impact angle can enhance or weaken the erosion loss. The fluctuation trend of impact angle was similar as that of erosion rate. The solid concentration had weak influence on the erosion pulsation characteristics and the erosion rate. The solid velocity had a significant effect on the erosion rate. The results can be used to provide guidance for numerical simulation of solid-liquid two-phase flow in pump.