Abstract: KM6 is the largest China's space environment test facility for manned spacecraft. It is one of five typical space environment test facilities in the world 9 sub system has been completed. The vacuum chamber consists of three parts. The main chamber is of 12m in diameter and 22 4m in height. Ultimate vacuum is 4 5×10 -6 Pa. Shroud temperature is 100K. It is of international advanced performance in the space environment simulation field. The paper describes the technical specification, systems, and performance characteristic. It provides test results. Important technical issues in the facility development are analyzed.