We design a multipurpose laser communication optical antenna to develop and debug the space multi-node laser communication system. The laser communication optical antenna and autocollimator can be switched when the lens or the optical beam splitter in the classic Cassegrain system is chosen. The primary mirror room is designed to improve the overall stiffness of the system and can be used as the lens hood of the system. The front end of the primary mirror room is connected with the disc-type secondary frame so as to assemble and debug the optical system conveniently. The primary mirror is fixed through six bonding points in the primary mirror room. The back end is connected with the backboard of the primary mirror room to provide the installation interfaces for lens assembly, optical beam-splitting assembly, and primary mirror auxiliary support. The finite element analysis results show that when the first order mode frequency of this structure is 345 Hz and the ambient temperature is 20 ℃±5 ℃, the root mean square (RMS) value of surface shape error of the primary mirror is less than λ/28. Tested by a 4D interferometer, the RMS value of wavefront aberration of the system is less than λ/14 under work mode of laser communication optical antenna, which can meet the requirements of laser communication system.