3D inverse design method was applied to configure the runner geometry of a middle-high head pump-turbine, in which design parameters were given according to pump operation and iterative calculations conducted from turbine direction. Model tests were performed to measure performances of developed runner under different operating modes and points. Test results show that the highest efficiency under pump mode is 91.34%, and highest efficiency under turbine mode is 88.5%. Internal flow analyses based on viscous full passage computations show that water pass through the passage smoothly with smaller loss under pump mode, while rather serious incidence loss exists at runner inlet and large low pressure area exists at suction side under turbine mode.