A matrix inversion obtaining method in an MMSE detection method comprises the steps of S1 setting a target inversion matrix A=D+E, wherein D is a diagonal matrix only containing the diagonal elements of a matrix A, E is a matrix of which the diagonal elements are all zero, and the elements at other positions are totally same as the elements of the matrix A; S2 adopting a formula as the initial estimation to be introduced in a formula (1) to obtain a formula (2); only considering P elements respectively at the left and right of the diagonal element at each row of the matrix E, wherein p is the expansion width, and setting the other elements as zero to obtain a strip matrix to calculate; then only carrying two iterations, thereby obtaining the final approximate evaluation of a matrix A<-1>. The method of the present invention has the advantages of being simple in principle, being easy to realize, being able to reduce the complexity and improve the calculation efficiency, etc.