With a low head hydropower station as case study, we observed and analyzed the influence of guide-wall design on the flow pattern at the intake of the station through physical model. Having theoretically analyzed the local vortex near the guide-wall, we presented the law of the formation of vortex near the guide-wall. Furthermore, based on numerical simulation of different working conditions through standard k-ε turbulence model, we analyzed the 3-D flow pattern, the section flow velocity distribution, and the turbulent kinetic energy to obtain factors affecting the flow pattern at the intake. We found that the length of guide-wall determined the lateral force on the vortex. Under certain hydraulic elements, when a critical value of guide-wall length exists, the head loss caused by vortex could be small while the discharge capacity could be optimum. This research could be referential for the design of guide-wall of power stations.