Abstract: Ultrahigh resolution imaging system on geosynchronous orbit can get earth image with 1 m resolution, using diffractive membrane optics. Cable -Strut Deployable Articulated Mast in this imaging system is about 100 m long, and was tightly required for its deformation. The diameter of primary mirror is about 20 m, and its thickness is only a few micrometers. To meet the optical performance objectives, the distortion of the primary mirror need to be minimized. So the thermal control system for Deployable Mast and primary mirror becomes a tremendous challenge. Based on the survey results about deployable baffle and primary mirror with large-scale membrane, ultrahigh resolution imaging system was thermally analyzed, and thermal control scheme was designed. The temperature distributions of deployable conical baffle in four extreme working conditions were provided, and the simulation results show the feasibility of the designed thermal control scheme.