The embodiment of the invention relates to a pitch gain obtaining method, a pitch gain obtaining device, a coder and decoder. The pitch gain obtaining method comprises the steps of obtaining the information of an input signal and obtaining pitch gain which corresponds to the information of the input signal according to the relevant relationship of the information of the input signal and the pitchgain. The embodiment of the invention is applicable to both a coding end and a decoding end by using the preliminarily gained corresponding relationship between the information of the input signal and the pitch gain and according to the corresponding pitch gain which can be gained by the information of the input signal, so that the coding end does not need to transfer the pitch gain to the decoding end, and the problem of the bit consumption is solved. The embodiment of the invention can adaptively confirm the pitch gain according to the information of the input information, avoids consuming extra bit to qualify the pitch gain, does not affect the coding performance and improves the compression rate.