The three dimensional unsteady turbulent flow in axial-flow pump whole flow field was simulated based on Reynolds time-averaged Navier-Stoke (RANS) solver embedded with k-ε turbulence model and SIMPLEC arithmetic. The pressure fluctuation under various operation conditions and different guide-vanes were obtained. Numerical and experimental results showed that the maximum amplitude of pressure fluctuation took place at the inlet of impeller. The amplitude of pressure fluctuation became stronger significantly as the flow rate was far from optimum operation point. At the outlet of guide-vanes the fluctuation amplitude increased when the number of guide-vanes reduced. The frequency of pressure fluctuation is dominated by the rotation speed of impeller and the number of guide-vanes has little affect on it.