Remote camera is confronted with complex space temperature environment during flying. The effective thermal design is performed for ensuring imaging qualities. Primary theories of thermal design for remote camera are introduced, and the influence and countermeasure on characteristic of the large off-axis triple-mirror anastigmatic camera for thermal design are analyzed. Finally in-orbit temperature is summarized. Based on the simulation method of thermal model, the temperature results of position without telemetry temperature are obtained. In-orbit analysis result shows that all temperature of primary parts for camera is in the range of 20 ℃±2 ℃. The validity of thermal design for camera is proved.