To locate payloads for the least significant bit matching (LSB-M) steganography, the paper proposes a new method. The problem of payload location for LSB-M can be solved by abstracting the mean square adjacency pixel difference feature of every pixel to classify all the pixels into two parts: payload or non-payload. The feature is proved effective both theoretically and experimentally. Furthermore, the proposed method is compared with the maximum a posteriori estimator for payload location aimed at LSB-M. When the embedding rate is low, the method performs much better than the maximum a posteriori estimator.