Based on the standard k-ε turbulence model and the RANS equations, the finite volume method and the SIMPLE algorithm were adopted to carry out the three-dimensional viscous numerical simulation of the intal flow within a vortex pump in double reference frames. According to the results of numerical simulation, the intal flow in the vortex pump was analyzed, and the calculated results of blade surface pressure of the impeller were compared with experimental results. The maximum relative error is 6.6% between calculated value and experimental value of the pump head under operation conditions.