In order to ensure the optical sensor working in altitude complex environment could gain the high resolution and high quality image, the thermal control design is presented. The design feature and thermal environment are analyzed, and the heat-transfer model is established. The coefficient of heat convection and aerodynamic heat are calculated in detail. According to the requirements of thermal control, the method of thermal control design is put forward.The transient thermal analysis is simulated with the IDEAS-TMG software, and the thermal balance tests and the thermal-optical tests are carried out to validate the design. The results of the simulation and tests show that the temperature level of lens component is 20 ℃±1.5 ℃ in 2 h, the axial temperature difference of lens component is no more than 3.1 ℃, the radial temperature difference of lens component is no more than 1.9 ℃, and the variation range of CCD component temperature is 20 ℃～29.4 ℃, satisfying the requirements. The photographic resolution of optical sensor is 51.5 lp/mm, also satisfying the design requirement. The results show that the thermal control design is feasible and reasonable. The method of thermal control design and tests discussed in this paper provides a certain reference to thermal design of other aerial remote sensor.