Numerical calculation was performed with 16 different conditions from 50%~120% of the design flow in shaft front-positioned and shaft rear-positioned tubular pump systems by using software Fluent 6.2. The Reynolds-averaged Navier-Stokes equations were discretized and solved with Spalart-Allmaras turbulence model and SIMPLEC algorithm. The results of numerical simulation were compared with model test data which was converted into the prototype size, and the result of the comparison showed that the tendency of performance change is in good agreement, the efficiency error between calculation data and model data is ±5% under the condition of the same flow. The basic flow pattern of inlet conduit, pump chamber and outlet conduit was analyzed and compared, and the reason for hydraulic loss was investigated. The results indicated that the flow pattern in the inlet and outlet conduit of the shaft front-positioned tubular pump system was good, and that the flow pattern in the inlet conduit of the shaft rear-positioned tubular pump was uniform and smooth. However, the flow pattern in the outlet conduit was in disorder. The hydraulic loss was relatively large, and the efficiency was lower; guide vane and shaft are the critical factors to affect the flow pattern of outlet conduit and arrangement efficiency, stall and vortexes are easily appeared under the influence of guide vane circulation and shaft.