To effectively evaluate the detection capability of the infrared search and tracking system (IRST), the mathematical models of target infrared (IR) radiation intensity envelope, atmospheric transmittance, and signal-to-noise ratio (SNR) operating range are improved, respectively. Based on the above three models, the IRST performance evaluation simulation system is designed to analyze the optimal detection point and effective detection area under different conditions (such as target speed, detection angle, detection probability, false alarm probability, and operating range). Meanwhile, in order to verify the validity of the model, the range evaluation method of calibration and cross-validation is proposed. And taking the cross-validation method as the baseline, the error of the optimized mathematical model of IRST in this paper is within 10%. The research results are of reference significance for IRST operating range evaluation, design, and use.