Abstract: Effective channel order estimation is a critical step of blind channel identification. A blind channel effective order estimation algorithm based on SubSpace Channel Matrix Recursion (SS-CMR) is proposed. On the basis of the special structure of Q matrix and the its null space vector equivalently viewed as the convolution of true channel impulse response and the common zero channel, the channel matrix is obtained by SS method and then the estimated channel order is got by the constructed recursion cost function. The simulation proves that the performance of SS-CRM is improved compared with CMR and obviously better than the other existing algorithm, especially when the channel impulse response has small head and tail taps; analytical analysis shows that the algorithm complexity of SS-CMR is obviously reduced compared with CMR.