We describe the method for optical design of afocal achromatic systems that keep their characteristics stable in a wide thermal range without refocusing. Usually, thermal stabilization of the back focal length of an optical system is considered, but these methods are not directly applicable for afocal systems. The method proposed is based on the idea of using a proper combination of optical materials and powers of optical elements to keep the whole system as an afocal one in the desired temperature range. As an additional advantage, the method has shown that afocal systems have enough parameters to achieve achromatic correction and may take into account the F-number of optical elements, which is important for the aberration balance. The research presents both theoretical statements and the example of a laser beam expander for dual wavelengths. The method can also be used to design afocal achromatic compensators that help to achieve thermal stability.