The direct detection of gravitational waves opens up a new era of gravitational wave astronomy, and 100-year-old prediction on gravitational wavers by Einstein have been confirmed ultimately. The space gravitational wave detector makes it possible to detect rich sources of gravitational waves in the 01 mHz-1 Hz band. The space gravitational wave detector and the ground gravitational wave detector complement each other, and the combination of the two methods can realize the detection of gravitational waves in a broader band, thus uncovering more secrets of the early universe. Spatial laser interferometry gravitational wave detection uses heterodyne interferometry to measure changes in the order of 10 pm between two free-floating test masses that are millions of kilometers apart. Telescope is an important part of the laser interferometry system. Unlike the traditional geometrical imaging telescope, the telescope of the laser interferometry system shall meet the requirements of optical path stability for 1 pm and that of a harsh stray light. Based on the mission requirements of the Taiji Program in Space, this paper analyzes the functions and technical requirements of the telescope and completes the preliminary design of the principle prototype. In this paper, the sensitivity of the telescope system is analyzed according to the wavefront distribution in the far field of one million kilometers. At the same time, the thermal integration simulation in orbit is completed, which lays the technical foundation for the development of the subsequent principle prototypes.