The algebra algorithm solving the linear combination characteristic of delayed m-sequence is discussed. Based on analysis of linear relationship between status of the central m-sequence and the delayed sequence, a new algorithm, which solves the multiplex problem of delayed m-sequence is given by taking advantage of linear equations over binary finite field. Application of this algorithm in the design of the mask of the N-CDMA mobile communication system is discussed. This algorithm provides a convenient way in solving the multiplex problem of long m-sequence in engineering calculation.