A novel earth observation space infrared camera has been successfully launched into orbit by a test satellite. The inclined-LEO orbit for the camera is not a sun-synchronous orbit, and thus the variation of external heat flux for the space load is extremely complicated. In order to guarantee the camera operating stably in orbit, high temperature stability for the optical system and the load-carrying construction and large power pulse tube cryocooler of low temperature infrared detector are both required. The complicated orbit heat flow and high stability thermal control indexes brought a big challenge for the thermal design. Based on the thermal control index and the space environment, the characteristic of the thermal design was analyzed and the team proposed a set of measures to meet the targets, like attitude maneuver, indirect radiant thermal control and coupled radiating surface. The thermal balance test result and in-orbit temperature data both indicated the thermal stability of the optical system was better than ±0.3 ℃ for each orbit within the temperature level of （18±2） ℃. Results shows that the thermal design is reasonable and practicable, and the space infrared camera works in good condition in orbit.