Abstract: In the present paper, based on the unsteady incompressible flow governing equations, the k-ε turbulence model and the SIMPLEC method, are used to simulate numerically the 3-D turbulent flow through the full flow passage in a Contra-Rotating Axial Flow Pump within a complete rotating period of the impeller. The results, such as the pressure distribution and isolines of velocity on the middle peripheral section and on the midway interaction surface in the flow passage, show respectively the variation of flow field characteristics in the front impeller, rear impeller and full flow passage in one rotating period. It is also indicated that the 3-D unsteady turbulent simulation is effective for understanding the contra-rotating flow field, as well as the interaction mechanism.