In order to comprehensively study the flow field characteristics of pumped storage power station’s whole flow system in pump mode, a geometric model of the flow system including diversion tunnel,surge chamber,penstock,pump turbine unit and tailrace tunnel was established. The flow characteristic in pump mode was simulated by control equations which considered gravity influence and shear stress transmission SSTk-ωmode. Hydraulic losses were calculated and analyzed based on the numerical results. Results showed that using the numerical simulation method considered gravity influence could get more realistic results with the efficiency error of 0.9% and lift error of 1.0% in the rated condition, which are less than 3.5% and 3.0% in other cases,respectively.Hydraulic loss of unit-block is significant,by contrast,it is small in the water conveyance system that takes up 10.4% of total hydraulic loss averagely.The main reason of unit-block’s hydraulic loss is different at different flow conditions with the same guide vane opening, flow pattern disordered at inlet of runner and asymmetric at outlet of runner intensified hydraulic loss at the low flow conditions,while the hydraulic loss at high flow conditions mainly because the opening of guide vanes is not big enough.
