A method and device for decoding a signal, where the method for decoding the signal includes obtaining spectral coefficients of sub-bands from a received bitstream by decoding, classifying sub-bands in which the spectral coefficients are located into a sub-band with saturated bit allocation and a sub-band with unsaturated bit allocation, performing noise filling on a spectral coefficient that has not been obtained by decoding and is in the sub-band with unsaturated bit allocation to restore the spectral coefficient that has not been obtained by decoding, and obtaining a frequency domain signal according to the spectral coefficients obtained by decoding and the restored spectral coefficient. Therefore, a sub-band with unsaturated bit allocation in a frequency domain signal may be obtained by classification, thereby improving signal decoding quality.