Orbit target IR characteristic is the basis of the IR imaging detection equipment design, the corresponding digital simulation model validation, and the application processing development, such as the target detection and tracking. In the work, an infrared measurement system for simulated space target is represented. The system can acquire the infrared characteristics of the target in the simulated space environment on the ground. In order to simulate the whole orbit environment, vacuum chamber and solar simulator are used in the work. An IR window is developed for the system. Then measurement instruments can be place outside the chamber to get the characteristic through the IR window. The work also provides a method to calibrate the IR window. The IR characteristic at the wavelength range of 3 μ~12 μm can be obtained with the system.