Assumed that the response to the blackbody radiation of the same temperature are equal for each pixel, each column of the infrared detector should have the same gain. But in practice, due to the defects of the production process and the material components of the focal plane array, the response of each pixel is not identical, meanwhile the channel gain of each column is not the same. The column channel gain non-uniformity of the readout circuit of the IRFPA was mainly studied. A lot of actual data was used for column channel output response curve fitting. Then, according to the data, the model of the polynomial curve simulate detector with column channel gain non-uniformity was deduced, and the precision analysis of the fitting curve was did, where a hypothesis testing method was used to verify whether the polynomial model was fit for the column gain of actual detector in global. Finally, a good simulation to the gain non-uniformity of each column was achieved.