1. A multi-stage quantization method, comprising: one of obtaining a reference codebook according to a previous stage codebook or codebooks from two or more previous stages, and combining vectors from the previous stage codebook to generate the reference codebook; obtaining a current stage codebook multiplying the reference codebook by a scaling factor; and quantizing an input vector by using the current stage codebook; wherein the scaling factor is found by bit mapping a quantization result of the previous stage, the quantization result of the previous stage comprises an energy parameter, the scaling factor is found by bit mapping a quantization result of the previous stage comprising: the scaling factor is found by bit mapping a higher n bits of a quantization index id_x E for the energy parameter, wherein, the idx_E totally has m bits, the higher n bits are idx_E>>(m−n) the sign ‘>>’ indicates the operation of right shifting, the mapped scaling factor is Y idx —E >>(m−n).