The number of space optical instruments is growing with a quick pace. Reflective mirror is always a significant part in a space optical system, especially in the laser communication system. Support is used to connect reflective mirror to other structure. The paper focused on designing a cylinder support. Considering thermal condition in space, the paper gave a special design of support with some soft links. The paper made a comparison between traditional design scheme of cylinder support and new design scheme of special cylinder support. From the comparison, it could be concluded that new design scheme had better performance in the thermal condition. Later, modal analysis and some vibration analyses were done to verify the reliability and feasibility of the new design. The result showed the design scheme was good. © 2021 COPYRIGHT SPIE.