Disclosed are a method and apparatus for decoding a an audiospeech signal using an adaptive codebook update. The method for decoding speech an audio signal includes: receiving an N+1-th normal frame data that is a normal frame transmitted after an N-th frame that is a loss frame data loss; determining whether an adaptive codebook of a final subframe of the N-th frame is updated or not by using the N-th frame and the N+1-th frame; updating the adaptive codebook of the final subframe of the N-th frame by using a the pitch index of the N+1-the frame; and synthesizing an audio a speech signal of by using the N+1-th frame.