1. A channel decoding method, comprising: performing, by a tail biting convolutional decoder, add-compare-select processing on metric values of 2 N states according to input data to be decoded and N zeros input after the data to be decoded to obtain final cumulative metric values of the 2 N states, and storing, by the tail biting convolutional decoder, a selection result of the add-compare-select processing, wherein N is a constraint length of tail biting convolutional coding; backtracking, by the tail biting convolutional decoder, from one state of the 2 N states according to the selection result to obtain an intermediate decoding result, after the add-compare-select processing is finished; and outputting, by the tail biting convolutional decoder, bits except last N bits of the intermediate decoding result as decoded result of the data to be decoded.