The main objective of the present article was to obtain the optimum structure of the plastic lined pump under the condition of fluid-structure interaction. The structural parameters of the pump were calculated according to the given design parameters. The three-dimensional geometric model was established. The flow field analysis was carried out by CFD. The inlet diameter 𝐷𝑗 , outlet width 𝑏2, vane outlet angle 𝛽2 and vane number 𝑍 of the impeller were selected as the four factors to design orthogonal experiment. The results were analyzed by range analysis. The efficiency and NPSH were obtained as combined parameters under the evaluation index. The genetic algorithm was used to optimize its structural parameters, and the best structural combination parameters of the plastic-lined pump under the conditions of maximum efficiency and minimum cavitation were obtained. The efficiency was increased by 2.78% and the NPSH was reduced by 0.249707 after optimization. Finally, the stress distribution and displacement deformation under the condition of the coupling field were obtained by the fluidsolid coupling analysis. The maximum stress was 4.83mpa and the maximum displacement deformation was 3.1547e-5m.