The invention provides an IntMDCT-based lossless audio encoding method and decoding method. The encoding method includes the following steps that: (1) audio time domain signals x (k) are framed, and a single frame of time domain signals x (k) can be obtained, wherein the k=0,..., N-1, wherein the N is frame length; (2) IntMDCT transformation is performed on the time domain signals, so that frequency domain signals X (m) can be obtained, wherein the m=0,..., N-1; and (3) Rice encoding is performed on the frequency domain signals, so that code streams can be obtained. The decoding method is an inverse process of the encoding method and includes the following steps that: firstly, Rice decoding is performed on an inputted code stream file, so that the frequency domain signals X (m) can be obtained, wherein the m=0,..., N-1; and secondly, IntMDCT inverse transformation is performed, so that the time domain signals x (k) can be restored, wherein the k=0,..., N-1. With the methods of the invention adopted, encoding parameters can be obtained adaptively, and the value of compression ratio is lower than that of block adaptive Rice, and the methods of the invention have a wider applicable range.