Abstract: With the guide vane of the pump-turbine as the main research object, the guide vane opening of 11, 33 and 41 mm is selected to analyze the influence of different guide vane airfoils on runaway characteristics of pump-turbine, so as to provide methods and theoretical guidance for the design and optimization of guide vane airfoil of pump-turbine. The results show that the improved guide vane airfoil has a better improvement effect on the "S" characteristics of the unit under three kinds of guide vane openings. After the improvement of the guide vane airfoil, the internal flow state of the unit is improved on runaway characteristics. The velocity streamlines in the guide vane and runner area are evenly distributed, and the concentrated distribution area of vortex core is reduced. After the improvement of guide vane airfoil, the relative value of pressure pulsation amplitude of monitoring points in vaneless area at different openings decreases in different degrees, and the velocity pulsation curve is gentle and the velocity peak value is smaller than before the improvement. The concentrated distribution area of vortex core in the draft tube of the improved guide vane airfoil is reduced, and the unit can operate in a relatively stable state.