The invention aims to provide an acoustic surface wave high-order nonlinear parameter representation method for a bending fatigue state of a metal plate, and the method is used for detecting the bending fatigue state of the metal plate in real time and predicting the bending fatigue life of the metal plate and is widely applied to the fields of aerospace, machinery, traffic, chemical engineering, water conservancy and the like. The method comprises the following steps: determining parameters of an excitation signal according to the surface wave transmission distance and the acoustic velocity of a detected material; emitting a pulse string signal by a high-power ultrasonic transceiver, enabling ultrasonic wave beam to be obliquely incident to the material to generate surface waves, and interacting the surface waves with fatigue defects such as microdefects, micro-plastic deformation or microcracks generated in a bending fatigue process to generate a higher harmonic signal; recording the change of nonlinear parameters every a fixed cycle in a bending fatigue test process, comparing with a standard curve, judging whether a test piece has defects or not, emitting an early warning signal, and predicting the residual bending fatigue life of the metal plate.