Abstract: Source number estimation based on information theoretic criteria can not be used in colored noise field,and the performance of the gerschgorin radii algorithm may decline under low signal-to-noise ratio (SNR) condition.In order to solve these problems,a method using the covariance matrix delay processing based on diagonal loading (DL) is proposed.First,the delay covariance matrix of the received data is constructed,the effect of colored noise is suppressed.Then a transformation processing is used for the delay correlation matrix,the eigenvalues of the covariance matrix are obtained after the inhibition of the noise.Finally,these eigenvalues are changed based on DL technique,and the information theoretic criterion is applied to estimate the source number.Computer simulation verifies the correctness and effectiveness of the proposed algorithm.