The present invention relates to a method and apparatus for obtaining a pitch gain, and a coder and a decoder. The method includes: obtaining information about an input signal; and obtaining a pitch gain corresponding to the information about the input signal according to the correspondence between the signal information and the pitch gain. The embodiments of the present invention obtain the corresponding pitch gain according to the signal information by using the obtained correspondence between the signal information and the pitch gain, and the pitch gain is applicable to the coder and the decoder, thus making it unnecessary for the coder to transmit the pitch gain to the decoder and solving the problem of bit overhead. The embodiments of the present invention determine the pitch gain adaptively according to the signal information, avoid consumption of extra bits for quantizing the pitch gain, avoid impact on the coding performance, and improve the compression ratio.