1. A channel decoding method, comprising: decoding, by a tail biting convolutional decoder, input data to be decoded; after the decoding of the input data to be decoded is completed, continuing to perform additional M steps of add-compare-select processing by using 0 as a path metric value on metric values of 2 N states to obtain final cumulative metric values of the 2 N states by the tail biting convolutional decoder, wherein M is more than or equal to N, and N is a constraint length of tail biting convolutional coding; backtracking, by the tail biting convolutional decoder, from any one state of the 2 N states 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 M bits of the intermediate decoding result as decoded result of the data to be decoded.