Using the standard k-ε turbulence model and the VOF method, numerical simulation of the lateral inlet and outlet, water pipelines and partial upper reservoir of a pumped storage power station was carried out. The effects of division pier layout on the hydraulic characteristics such as the flow rate distribution at the inlet and outlet, the split coefficient of channels, head loss and the flow distribution near the pier head were analyzed under the condition of dead water level. The result shows that, the retro-position of the middle division pier has little influence on the velocity distribution, the split coefficient and the head loss under power generation condition. In the pumping operation mode, the uniformity of velocity and split ratio can be improved, and the head loss can be reduced. However, the improvement is less obvious if the retro-position range is 0. 3 times larger than the initial section of the diffuser. The uniformity of the local velocity near the pier head can be realized if the retro-position of the middle division pier and the side division piers is 0. 44 to 0. 52 times and 0. 1 times the width of the initial section of the diffuser, respectively. The optimization of hydraulic characteristics can be achieved when the retro-position of the middle division pier and the side division piers is 0. 5 times and 0. 1 times the width of the initial section of the diffuser, respectively.