A set of horizontal ultra-long comprehensive test platform for high vacuum environmental simulation is designed in this paper, including vacuum chamber, vacuum pumping system, thermal simulation system, cooling water circulation system and other auxiliary support systems. The environmental simulation system is mainly used to provide conditions for the vacuum environment test, and meet the requirements of key technical indicators during the test process, meanwhile realize the calibration for the target movement trajectory within a clear imaging distance, thus provide technical and test data support for the development and improvement of subsequent projects.