A stereo encoding method, characterized in that the method comprises: obtaining a left channel energy relation coefficient between a first monophonic signal and a left channel signal; obtaining a right channel energy relation coefficient between the first monophonic signal and a right channel signal; the method being characterised by obtaining energy sums of predicted values of left and right channel signals at a wave trough by using the first monophonic signal and left and right channel energy relation coefficients respectively, wherein left and right channel signals are downmixed into one monophonic signal, the monophonic signal is converted to a Modified Discrete Cosine Transform, MDCT, domain, the monophonic signal in the MDCT domain is encoded, and local decoding is performed to obtain a monophonic signal which is the first monophonic signal; obtaining cross correlation results between the predicted value of the left channel signal at the wave trough and the left channel signal and between the predicted value of the right channel signal at the wave trough and the right channel signal, by using the first monophonic signal and the left and right channel energy relation coefficients respectively, wherein the predicted value of the left channel signal is the product of the first monophonic signal and the left channel energy relation coefficient, the predicted value of the right channel signal is the product of the first monophonic signal and the right channel energy relation coefficient; obtaining a scaling factor by using the energy sums of the predicted values of the left and right channel signals and the cross correlation results between the predicted value of the left channel signal and the left channel signal and between the predicted value of the right channel signal and the right channel signal; and encoding the stereo left and right channel signals according to the scaling factor. obtaining a left channel energy relation coefficient between a first monophonic signal and a left channel signal; obtaining a right channel energy relation coefficient between the first monophonic signal and a right channel signal; the method being characterised by obtaining energy sums of predicted values of left and right channel signals at a wave trough by using the first monophonic signal and left and right channel energy relation coefficients respectively, wherein left and right channel signals are downmixed into one monophonic signal, the monophonic signal is converted to a Modified Discrete Cosine Transform, MDCT, domain, the monophonic signal in the MDCT domain is encoded, and local decoding is performed to obtain a monophonic signal which is the first monophonic signal; obtaining cross correlation results between the predicted value of the left channel signal at the wave trough and the left channel signal and between the predicted value of the right channel signal at the wave trough and the right channel signal, by using the first monophonic signal and the left and right channel energy relation coefficients respectively, wherein the predicted value of the left channel signal is the product of the first monophonic signal and the left channel energy relation coefficient, the predicted value of the right channel signal is the product of the first monophonic signal and the right channel energy relation coefficient; obtaining a scaling factor by using the energy sums of the predicted values of the left and right channel signals and the cross correlation results between the predicted value of the left channel signal and the left channel signal and between the predicted value of the right channel signal and the right channel signal; and encoding the stereo left and right channel signals according to the scaling factor.