Abstract: An improved non-iterative multiple signal classification (INI-MUSIC) algorithm was proposed to solve the problem of low estimation accuracy of rotation iterative algorithm under the condition of mixed mutual coupling error and amplitude gain error. The improved algorithm used the special properties of the error coefficients under a uniform circular array and the matrix-vector conversion theorem to separate the amplitude-phase error and the mutual coupling error from the DOA estimation, so as to realize the dimension reduction operation under the mixed error. Then the cost spectrum peak function was reconstructed to compensate the loss of rank and to obtain the estimation of the DOA angle and the joint estimation of the error coefficient. The probability of error spectrum peaks was reduced by the proposed algorithm, which has better two-dimensional DOA estimation accuracy, and has higher engineering application value.