In order to improve the estimation accuracy of noise model and the rate-distortion performance of the sys-tem，an adaptive noise model estimation method on the basis of residual sub-band grouping is proposed． In this method，firstly，residual sub-bands are grouped according to their frequencies． Secondly，feature vectors are generated from the residual coefficients of all sub-bands in the same group． Then，the coefficients in each sub-band are clustered into different classes by means of improved fuzzy c-means clustering． Finally，the noise para-meters of each class of residual coefficients are estimated successfully． Experimental results show that，in compari-son with the method on the basis of adjacent sub-band clustering and variance estimation，the proposed method matches the residual distribution characteristics more accurately，improves the average rate-distortion performance by 0. 60dB，and saves the decoding time by 40. 59%．