Abstract: Abstract: Axial-flow pump is widely used in Chinese agricultural production. Guide cone as an important component of impeller for axial-flow pump can enhance the flow quality of pump inlet. To find feasible design method of guide cone, investigate the influence between flow field of guide cone and that of impeller and make a preliminary exploration about rounding way of guide cone, the flow passages about six different types of guide cone with impellers were numerically simulated. The numerical simulation was based on the three dimensional incompressible Navier-Stokes equation and k-ε turbulent model. SIMPLEC algorithm was applied to solve a discretization governing equation. Velocity of the calculation model was 2.92 m/s, and pressure of outlet was 101325 Pa. The design parameters of impeller included 5 blades, design flow of 330 m3/h, head of 5.1 m, rotating speed of 1450 r/min, diameter of impeller of 200 mm, and hub diameter of 118 mm. Based on a laboratory test performed on a DN200 test bench to measure the pumping head, discharge, and other parameters for calculation of head and efficiency, we found that the simulated and measured head and efficiency had relative error less than 4%, indicating the feasibility of the simulation method for flow field simulation of guide cones. After cooperating with the impeller, the flow field simulation results of guide cone showed that the Witozinsky guide cone was best with the highest impeller hydraulic efficiency but the circular guide cone was worst with the lowest impeller hydraulic efficiency. It indicated that the better exit flow field the guide cone flow passage had, the higher hydraulic efficiency of axial-flow pump impeller was. The rotating of impeller had effects on the uniformity of axial velocity distribution in the export section of cone flow field, but the effect of head loss and velocity weighted average drift angle was very small. The rotating of impeller also had effects on the axial-velocity distribution of outlet flow field, and little influence on radial-velocity distribution. The short distance between export section of cone with the impeller tended to increase the influence of the impeller rotating on the cross section. Appropriate increase of guide water cone length could improve the hydraulic efficiency of the impeller and the uniformity of axial velocity distribution, reduce the velocity weighted average drift angle and turbulence intensity of the export section of guide cone flow field. However, with increasing the length of guide cone, the hydraulic loss of guide cone would increase. Based on the results above in combination with practical application, we suggested that the optimal length of the guide cone with impeller was 0.5-0.7 times as impeller diameter. Meanwhile, the study showed that the adverse pressure gradient caused by the water cone sharp head could decrease the velocity of guide cone flow, which could induce the flow separation and flow disturbance. So the roundness of the water cone sharp head was necessary. After investigating the rounding coefficient, we found that the increase of water cone round length was able to reduce the hydraulic loss of guide cone and improve the impeller hydraulic efficiency. After tentative exploration, we suggested that the optimal round length of guide cone was 1/8-1/7 times as length of guide cone. The study has very important significance for the optimal design of axial-flow pump hydraulic model and the large-scale pumping station renovation.