In order to study the flow field of the Expendable Current Profiler(XCP) probe, based on the 3D Navier-Stokes equations for viscous unsteady incompressible flow, two- equation turbulence models are applied, the interaction flow field over the XCP probe is numerically simulated by implicit finite volume methods. The motion characteristics of the XCP probe are analyzed based on the flow field, especially, the flow field at the probe's tail and head. The simulated results show that the flow field is symmetrical, and the flow separation does not occur around the XCP probe. The laminar boundary layer is transformed into the turbulent boundary layer, which appears in the front-end 10cm of XCP probe. The head of the probe's arc design plays a very important role in the rapid and steady falling. The probe's tail has no advantage for fast falling, but contributes in keeping the vertical falling stance. These results verify the feasibility and effectiveness of this numerical analysis method and also provide a guidance for the optimization design of similar probes.