The nonlinearity introduced by the detector of atmospheric vertical sounder (AVS) is analyzed. The comparison between the ideal interferometric data and the simulated interferometric data with quadratic nonlinearity is conducted, and the influence of quadratic nonlinearity on spectrum is illuminated. The correction to quadratic nonlinearity in the practically acquired interferometric data is performed and the corrected data are adopted to the radiation calibration of AVS. The experimental results indicate that the goodness-of-fit of calibration curves after data correction is approximately increased by 0.3%. The data after correction are more accurate than before in the two-point calibration on stars.