Smoke screen,characterized by its cost effectiveness and ease of deployment,is one of the most efficient passive countermeasures in electro optical for countering precision guided weapons.However,existing evaluation indexes for smokescreen jamming efficiency are predominantly focus on the inherent jamming performance of the smokescreen materialsthemselves,with limited consideration of the interaction mechanisms between smokescreen and their targets.To address this gap,an analysis is conducted onthe impact of smokescreens on the image quality of infrared imaging guidance systems.Based on image grayscale features and structural similarity features,and incorporatingthe local occlusion characteristics of the smoke screen on target images,a Local Feature Weighted Structural Similarity (LFWSIM) index is innovatively proposed.And the applicability of the index is verified through field experiments.The experimental results demonstrate that LFWSIM overcomes the limitation that the attenuation rate is not suitable in scenarios where target area luminance abruptlychanges before and after smokescreen deployment.Compared with the Pearson Linear Correlation Coefficient (PLCC),Structural Similarity (SSIM) and Complex Wavelet Structural Similarity (CW SSIM),the LFWSIMdemonstrates greater sensitivity to smokescreen jamming,with greater amplitudes of numerical variations that are consistent with the actual smokescreen jamming effect.Moreover,when the target area is fully obscured by smokescreen,the LFWSIMcorrelation exhibits a standard deviation of 0.053,indicating superior stability and better consistency with human visual perception.