To analyze the influence of aeronautical low temperature on the self-collimation focus detection system, and enables the design and correction of the actual focus detection system, the relationship among various factors under different imaging conditions was investigated. Based on the principle of autocollimation focus detection and geometry, comparison of single-point and fringe imaging, imaging position and width according to different received light intensities, and presence and absence of astigmatic conditions were analyzed. Thus, a related analysis formula was deduced.Combined with the actual camera working conditions, the corresponding simulation of the optical system was performed, and the simulation results (simulated bimodal voltage values of 1.4 V and 0.47 V) were in accordance with the actual test data (peak-to-focus double-peak voltage values of 1.38 V and 0.56 V). The actual modification measures are carried out to improve the temperature adaptability of the self-collimation detection system.The temperature adaptability analysis is in accordance with the actual demand and has a guiding function for the temperature adaptability of the system.