As the main detection tool in multi-field, large-aperture optoelectronic devices are characterized by strong detection capability and high resolution. However, limited by the optical principle, such devices show a strong dependence on precise focusing. Temperature focusing is a key operation for maintaining image quality. First, this study analyzes the theoretical relation between the temperature and the equivalent focal length of the system. Then, the shortcomings of the traditional compensation model are obtained via simulations. To accurately model the relation between the temperature and the focal length, the first-order Fourier function model is introduced for compensating the change in the focal length owing to the temperature. Finally, the linear compensation model and the first-order Fourier function model are compared based on application data. Results show that the fitting accuracy of temperature and focal length for first-order Fourier function model is higher than that for the linear compensation model. The first-order Fourier function model is simple and easy to implement. Moreover, it can be used for test and design of large-aperture optoelectronic devices and for temperature focusing.