The performance of centrifugal pumps are affected by impeller geometry parameters. Detached Eddy Simulation (DES) was used to simulate the flow field of a multistage centrifugal pump. The obtained numerical results are compared with the experimental ones, and the outcome shows an acceptable agreement. In order to investigate the effect of structural parameters on the pump performance, this numerical solution is carried out for different cases of impeller geometry, such as outlet angel, wrap angle, outlet width and blade numbers. The results showed that the outlet angle, outlet width, blade numbers were positive correlated with head, while wrap angle was negative correlated with head.