The invention discloses a signal source number estimation method based on Gerschgorin circle transformation and modified Rao score inspection. The method comprises the steps: firstly, calculating a sample covariance matrix of an observation signal; then, carrying out Gerschgorin circle transformation on the sample covariance matrix, and by utilizing the estimated value of the characteristic valueof the sample covariance matrix obtained after transformation and on the basis of the modified Rao score inspection thought, detecting the structural characteristics of the large-dimensional covariance matrix; and then, by detecting whether the covariance matrix of the noise part in the observation signal is in direct proportion to a unit matrix, constructing an observation statistical magnitude used for establishing an information theory criterion likelihood function, wherein the statistical magnitude is also the statistical magnitude of a sample characteristic value; and on the basis, carrying out signal source number estimation through a generalized Bayesian information criterion. The method provided by the invention has relatively wide applicability, is suitable for signal source number estimation under a classic asymptotic system, and is also suitable for signal source number estimation under a common asymptotic system; and the method is suitable for signal source number estimation in a white Gaussian noise environment and is also suitable for signal source number estimation in a color noise environment.