As for the non-uniformity of infrared images,the causes of occurrence of non-uniformity are analyzed theoretically.The EM algorithm of model-free image correction based on SG filter pretreatment is improved,and a single-frame image correction method of improving LSNR is proposed.A comparative experiment is designed,under the scenes of infrared target,dim target and cloud background,the method can reduce the non-uniformity (NU) of the infrared image by 56.869 3%,85.938 4% and 87.886 3% respectively, and increase the LSNR by 3.687 7 dB,0.256 9 dB and 3.553 1 dB respectively.Finally,the Gaussian-distributed target is superimposed on the non-uniformity background for simulation,and the relationship between the size of the target and the filtering window is discussed.The approximate relationship between the filtering window and the small infrared target is obtained as follows:H≈4.6*ST+0.3,and the selection of the initial value of the methods filtering window is determined from practical engineering applications.The results show that the proposed method can effectively correct the non-uniformity by using the scene information of a single-frame infrared image on the premise of maximum LSNR.