Disclosed is a method and device for realizing quantification in coding/decoding, which mainly comprises: firstly, quantification used in image switching coefficient matrix adopts quantification form of parameter model, the parameter model is a parameter model which needs only several parameters to present and it includes a frequency band distributing structure and frequency band parameters. Thereby, the quantified matrix satisfying human eye visual properties is obtained by the control of several parameters, and the subjective quality of image after coding is controlled and quantified; secondly, the method does not need to transmit or memorize the quantified matrix in codes flow, thus the coding efficiency is improved; finally, for the quantified computation of the image switching coefficients, this method can well adapt to the character of the content information in the image. Thus, this invention can improve subjective quality of the image after quantified coding.