A decoding method, comprising: receiving a to-be-decoded signal; performing region decision on the to-be-decoded signal according to a region decision rule formed by S region decision formulas on the IQ plane, to acquire a region decision result, wherein S is a positive integer and is less than the total number of constellation points comprised in N subsets that are used as a basis for generating the to-be-decoded signal at an encoding end, N is a positive integer greater than 1, every two constellation points in each subset are separately located in two different regions that are divided by using at least one decision formula in the S region decision formulas, and constellation points in the constellation diagram are divided into N subsets; acquiring N constellation points according to the decision result, wherein the N constellation points are separately constellation points that are in the N subsets and that are closest to the to-be-decoded signal; acquiring N non-encoded bits corresponding to the N constellation points, and branch metrics between the to-be-decoded signal and the N constellation points; and performing Viterbi decoding based on the branch metrics and the N non-encoded bits, and outputting a decoding result corresponding to the to-be-decoded signal; wherein the performing region decision on the to-be-decoded signal according to a region decision rule formed by S region decision formulas, to acquire a region decision result is characterised by: performing horizontal translation and rotation processing on the to-be-decoded signal according to the S region decision formulas, determining whether an imaginary part of the to-be-decoded signal is greater than 0, and acquiring S region decision results according to a determining result. receiving a to-be-decoded signal; performing region decision on the to-be-decoded signal according to a region decision rule formed by S region decision formulas on the IQ plane, to acquire a region decision result, wherein S is a positive integer and is less than the total number of constellation points comprised in N subsets that are used as a basis for generating the to-be-decoded signal at an encoding end, N is a positive integer greater than 1, every two constellation points in each subset are separately located in two different regions that are divided by using at least one decision formula in the S region decision formulas, and constellation points in the constellation diagram are divided into N subsets; acquiring N constellation points according to the decision result, wherein the N constellation points are separately constellation points that are in the N subsets and that are closest to the to-be-decoded signal; acquiring N non-encoded bits corresponding to the N constellation points, and branch metrics between the to-be-decoded signal and the N constellation points; and performing Viterbi decoding based on the branch metrics and the N non-encoded bits, and outputting a decoding result corresponding to the to-be-decoded signal; wherein the performing region decision on the to-be-decoded signal according to a region decision rule formed by S region decision formulas, to acquire a region decision result is characterised by: performing horizontal translation and rotation processing on the to-be-decoded signal according to the S region decision formulas, determining whether an imaginary part of the to-be-decoded signal is greater than 0, and acquiring S region decision results according to a determining result. performing horizontal translation and rotation processing on the to-be-decoded signal according to the S region decision formulas, determining whether an imaginary part of the to-be-decoded signal is greater than 0, and acquiring S region decision results according to a determining result.