The invention relates to the technical field of mechanical fault diagnosis, pattern recognition and the like, in particular to a gearbox fault diagnosis method and system based on singular value spectrum manifold analysis. The method comprises the steps: acquiring a fault vibration signal of a gearbox and preprocessing the signal to form a plurality of one-dimensional original vibration signal data, carrying out phase space reconstruction processing to obtain a plurality of two-dimensional matrixes; carrying out singular value decomposition on the reconstructed two-dimensional matrixes to obtain a singular value spectrum of the two-dimensional matrixes; calculating a slope of the singular value spectrum to obtain manifold characteristics of the singular value spectrum; training a support vector machine by adopting the characteristic data and constructing a fault diagnosis model; and inputting vibration signal data of a to-be-tested gearbox into the fault diagnosis model and outputtinga fault diagnosis classification result of the to-be-tested gearbox. According to the invention, the characteristic extraction of fault data of the gearbox is realized by using the singular value spectrum manifold analysis; the change trend of signal components can be effectively extracted; the influence of noise can be removed; the characterization capability of faults by characteristics can be enhanced; and the gearbox fault diagnosis precision can be improved.