The temperature increase of homing head caused by thermal radiation increase under high-energy laser irradiation, severely affects the signal-to-noise ratio (SNR) and imaging quality of optical systems. To address this issue, this study simulates an optical system of a roll-pitch infrared homing head in the 3?5 μm band, focuses on the temperature effects on the optical system under high-energy laser irradiation, and explores the impact of the internal temperature rise on the infrared homing head performance. Results show that as the internal temperature rises from 293.15 K to 1073.15 K, the SNR of the optical system decreases from 8.73 to ~0, causing the homing head to completely lose its target recognition capability. Thus, this research emphasizes the need to focus on the thermal stability of optical components when designing homing head systems to ensure their imaging quality and guidance precision during operation. This study not only helps improve the current design of homing heads but also provides a theoretical foundation for the development of subsequent high-energy laser defense systems.