The invention relates to a blade fault diagnostic method based on a strain energy response of a wind-driven generator, which comprises the following steps of: (1) obtaining the natural frequencies and the modes of the first M orders of the blade of a wind generator set by performing dynamic modeling and model analytical calculation to the wind generator set; (2) simulating the rotational excitation load of the blade through finite element calculation to the wind generator set to obtain strain energy time domain responses corresponding to the cabin sensor set points of the first M orders of the blade of the wind generator set, and then calculating strain energy frequency domain responses; and (3) obtaining the running state characteristic values of the blade of the wind generator set from the strain energy frequency domain responses corresponding to the cabin sensor set points of the first M orders of the blade of the wind generator set through the strain energy and the rate of change thereof and the method of a support vector machine, and then comparing to obtain a diagnostic result. The blade fault diagnostic method based on the strain energy response of the wind-driven generatorrelated to the invention is simple and easy, high in sensitivity and accuracy and low in diagnostic cost, and can effectively improve the safety and reliability of the blade of the wind generator setand accurately perform fault point positioning, fault qualification and prediction for the blade.