Aiming at improving the validity of blind dispreading DS-SS signal, the blind spread-spectrum and information sequence estimation of DS-SS signals is studied in this paper. Based on double PN periods, a new method of blinding estimate PN sequence and information sequence jointly was presented. The advantage of the algorithm is that it can estimate the PN sequence and information sequence jointly, with less computational cost. Compared with the traditional methods, this algorithm avoids the problem of phase ambiguity when the whole PN sequences are reconstructed using the two parts of spread-spectrum waveforms, which can highly improve the validity of blind estimation. The simulation results verify the validity of this algorithm.