The invention discloses a high-cycle fatigue test method and device for large blades of a gas turbine. The test device includes a fatigue test machine, a pressure head and a blade test piece clamp, wherein the clamp is composed of an L-shaped support frame, left and right pressure blocks, connecting and fixing bolts and a positioning pin. A blade test piece is fixed by the left and right pressingblocks and the connecting bolt, and then is fixed and positioned by the fixing bolt, the positioning pin and the L-shaped support frame side plate. The L-shaped support frame is fixed by a bottom plate waist shape and a fatigue test machine lower clamp. A upper clamp applies load to the top of the blade test piece by the pressure head. On the basis of the test device, through the analysis of the gas turbine blade load spectrum, the design and processing of the blade test piece, the design of a special clamp, and the loading spectrum design of the fatigue test machine, the high-cycle fatigue test of the fatigue weak part of the large blades of the gas turbine can be performed by using the general fatigue test machine, which is close to the actual conditions to achieve high-cycle fatigue performance checking.