Abstract: Abstract: Because flow separation of blade entrance region and low pressure area are located in the inlet of runner at pump mode, and the low pressure of blade at turbine mode usually occurs in the outlet of runner, the low pressure edges of runner are more risks of cavitation compared with other parts for pump-turbine. In this study, first of all, we proposed a two-order polynomial to describe the blade setting angle distribution law along the meridional streamline in the streamline equation. The runner was designed by the point-to-point integration method with a specific blade setting angle distribution with a consideration of the working condition of turbine and the working condition of pump by adjusting the blade setting angle of heading-edge and trailing-edge. By use of this method, we designed three blades with different position of low pressure edge. Secondly, based on SST k-ω turbulent model and Zwart cavitation model, steady and cavitation simulations at three turbine operations with different output were conducted such as 42% output (guide vane angle was 10°, unit discharge was 0.271 m3/s), 88% output (guide vane angle was 18°, unit discharge was 0.0562 m3/s), and 100% output ((guide vane angle was 22°, unit discharge was 0.649 m3/s). In addition, three pump operating conditions with different discharge in the same guide vane opening were selected to conduct steady and cavitation simulation. The pump operating condition was small discharge 0.79Qrp, and design discharge Qrp, and large discharge 1.24 Qrp. The computational boundary conditions were applied at the inlet and outlet surfaces of the computational domain. For the inlet boundary condition, a uniform velocity distribution was assumed. As for the outlet boundary condition, the average pressure was set constant. For the surface of a wall, the non-slip boundary conditions was prescribed, the velocity components were set to zero. Furthermore, concerning the interaction of the flow between a stator and rotor passage, Frozen Rotor interfaces were used. Finally, comparisons of energy performance, cavitation morphology and flow characteristics among runners were analyzed. Our results showed that the shift forward of low pressure edge within certain limits could eliminate the flow separation on the inlet of runner blade at large discharge pump condition, and as such it improved the head of pump and the cavitation performance of runner at large discharge pump condition. The shift backward of low pressure edge within certain limits could make the inlet flow of runner blade more uniform at small discharge pump condition, and therefore, it improved the cavitation performance of runner at small discharge pump condition. At turbine design condition, the outlet velocity circulation of low pressure edge 1 runner was close to zero, but the cavitation performance in both turbine and pump mode was not ideal. The outlet velocity circulation of low pressure edge 2 runner at band location was close to zero, and at crown location was a small negative value. The cavitation performance of low pressure edge 2 runner was the best. There was no cavitation in design turbine condition and full load turbine condition, and only slight cavitation was appeared at the design pump condition. The outlet velocity circulation of low pressure edge 2 runner at crown location was close to zero, and at band location was a small negative value, the cavitation performance of low pressure edge 3 runner was worse than that of low pressure edge 2 runner. The obtained results provide a good experience in the design of the pump turbine.