The contribution tothermal stability of an optical system made by the thermal expansion of lens housing mustbe considered in the design of an athermal space optical system. Each component of anoptical system can be determined by solving the equations based on the power of system,athermal and achromatic requirements. An athermal space system can be designed by a way ofabberation correction upon condition of fixed power of the components. The thermal affectof optical system of the reflective imaging spectrometer was analysed. The athermalobjective of an imaging spectrometer was designed by using this optical-mechanical-thermalintegrated design technique.