The invention discloses a power grid abnormality quick detection method based on a random matrix spectral radius method, and the detection method comprises the steps: carrying out the data collection of a power transmission line through a PMU, constructing sampling matrixes X, carrying out the standardization processing of the sampling matrixes X, carrying out the multiplying operation of L sampling matrixes X after standardization processing, obtaining a matrix Z, carrying out the standardization processing of the matrix Z, calculating the characteristic root of the matrix Z, carrying out the spectral distribution analysis, calculating the inner circle radius of the characteristic root, carrying out the judgment of the inner circle radius according to a threshold value boundary, and judging whether there is an abnormality or not. According to the invention, the method achieves the real-time quick global processing of data collected by the PMU, can accurately distinguish an abnormal weak signal, is high in sensitivity, enables the detection time to be remarkably ahead of the abnormality occurrence time, and can greatly improve the abnormality analysis and processing level of a power grid.