Embodiments of the present invention provide a method and device for demodulating data. The method includes: determining a number of reliable bits of each path of data in M paths of data and a modulation manner used to demodulate the reliable bits of each path of data, where M is a positive integer; demodulating the reliable bits of each path of data according to the modulation manner used to demodulate the reliable bits of each path of data; and demodulating residual bits in each path of data except the reliable bits according to a maximal likelihood ML algorithm. Compared with the prior art, it is unnecessary to demodulate all bits of each path of data according to the ML algorithm, thereby lowering the complexity of demodulation by using the ML algorithm.