A signal demodulation method, comprising: obtaining a receive signal and a symbol probability parameter of the receive signal, wherein the symbol probability parameter comprises: an amplitude r y and a phase angle φ y of the receive signal, an amplitude r x j and a phase angle φ x j of each constellation point x j in a decision constellation point set, and a standard deviation σ n of Gaussian noise and a standard deviation σ θ of phase noise, wherein the decision constellation point set is located in a modulation constellation graph required for performing signal demodulation (step 501); calculating, according to the symbol probability parameter, a symbol probability that a transmit signal corresponding to the receive signal is each constellation point x j in the decision constellation point set (step 502); and performing demodulation according to the symbol probability, and outputting demodulation information, wherein the demodulation information corresponds to a data bit corresponding to the transmit signal (step 503), wherein in case of performing a hard decision demodulation the demodulation information is a data bit corresponding to the transmit signal and in case of a soft decision modulation the demodulation information is soft information used to generate a data bit corresponding to the transmit signal, characterised in that the symbol probability that a transmit signal corresponding to the receive signal is each constellation point x j in the decision constellation point set is calculated according to the following formula: Pr x = x j / y = r y 4 πσ n exp − r y − r x j 2 2 σ n 2 − r x j r y φ y − φ x j 2 2 v j / v j, wherein the v j = r xj r y σ θ 2 + σ n 2, and the Pr ( x = x j / y) is the symbol probability. obtaining a receive signal and a symbol probability parameter of the receive signal, wherein the symbol probability parameter comprises: an amplitude r y and a phase angle φ y of the receive signal, an amplitude r x j and a phase angle φ x j of each constellation point x j in a decision constellation point set, and a standard deviation σ n of Gaussian noise and a standard deviation σ θ of phase noise, wherein the decision constellation point set is located in a modulation constellation graph required for performing signal demodulation (step 501); calculating, according to the symbol probability parameter, a symbol probability that a transmit signal corresponding to the receive signal is each constellation point x j in the decision constellation point set (step 502); and performing demodulation according to the symbol probability, and outputting demodulation information, wherein the demodulation information corresponds to a data bit corresponding to the transmit signal (step 503), wherein in case of performing a hard decision demodulation the demodulation information is a data bit corresponding to the transmit signal and in case of a soft decision modulation the demodulation information is soft information used to generate a data bit corresponding to the transmit signal, characterised in that the symbol probability that a transmit signal corresponding to the receive signal is each constellation point x j in the decision constellation point set is calculated according to the following formula: Pr x = x j / y = r y 4 πσ n exp − r y − r x j 2 2 σ n 2 − r x j r y φ y − φ x j 2 2 v j / v j, wherein the v j = r xj r y σ θ 2 + σ n 2, and the Pr ( x = x j / y) is the symbol probability.