The prediction of infrared extinction performance is one of the indispensable factors for the research of smoke screen. So far, it is still short of an accurate numerical simulation for the infrared extinction performance after releasing smoke screen. We present a method for calculating the infrared extinction performance of smoke screen. The standard k − ε turbulence model and the concentration equation of smoke screen are combined to carry out numerical simulation research on the sedimentation and diffusion process of smoke screen in the field. The shape and mass concentration distribution of smoke screen are studied under different wind speeds and ground roughness. Lambert–Beer’s law is combined to calculate the infrared extinction area of the smoke screen under different conditions, and the influence law on the smoke screen extinction performance is analyzed under different conditions. The validity of the numerical simulation results is verified by the field test. It is a useful method for guiding the design of field experiments. This work is widely used in the evaluation of extinction performance and provided more information for use by decision makers.