The 3-D dynamic meshing technique is applied for the numerical simulation of unsteady flow fields in a centrifugal pump using the Fluent software. The surface motion of the impeller in the computational domain is defined by the profile file in the Fluent software, in which the rotational direction and the speed of the impeller are specified. The simulation results are compared with those obtained by the widely used sliding mesh technique to illustrate the superior computational efficiency of the dynamic mesh method. In the dynamic mesh technique, all computational domains, considered as stationary, are defined in an inertial reference frame, while the topological relationships between the previous and the current mesh nodes are retained to ensure a good precision and time coherency. Three methods, namely the spring-based smoothing, the dynamic layering and the local re-meshing are used to cope with mesh deformations. Comparisons of solutions with those obtained by using the sliding mesh technique with an identical computational model, the same meshes, and initial and boundary conditions show that the results of both methods converge to comparable solutions within five revolutions of the impeller. The iterative speed of the dynamic mesh method, however, is almost three times of that of the Sliding Mesh method. The results thus suggest that the dynamic mesh technique for the flow simulation in centrifugal pumps, defined in an inertial reference frame, yields a substantially better computing efficiency than the sliding mesh method involving a comprehensive data transfer among multiple reference frames. This work shows that dynamic mesh technique can be used for numerical simulations of a three-dimensional unsteady flow field in pumps and has a strong versatility and broad application prospects.