As an infrared standard source, surface blackbody is widely used in infrared temperature measurement, infrared imaging, infrared camera calibration and other fields. The infrared radiation performance of infrared standard source mainly depends on the control of surface blackbody temperature field. In order to meet the development needs of large aperture and large field of view of spaceborne and airborne infrared detectors, the temperature control technology of extra large surface blackbody is studied in this paper. Under the condition of outfield, the difficulty of temperature control increases with the increase of surface blackbody size. The temperature control system adopts the two-phase fluid loop technology to realize the high temperature uniformity and stability temperature control of a 3 m×3 m surface blackbody for the outfield field under different target temperatures. The experiment results show that the surface temperature uniformity control of the black body is better than ±0.60 ℃ and the stability control is better than 0.14 ℃/15 min.