2.2 external environment, equipment, facilities, organization and management, many objective factors will also affect the stability of metro power supply system, such as external environment, power supply equipment quality, power supply system management, etc. . In the process of social development, many advanced power supply equipments have been used in metro power supply system. In the process of subway construction, the quality of power supply facilities, the advanced level of equipment and service life will affect the security and reliability of power supply system. In addition, the scientific management system to achieve long-term stability of the power supply system. At present, both the management level of the power supply system manager and the improvement of the management system can not keep up with the long-term stability of the power system. In order to improve the safety and stability of effective subway power supply system, it is necessary to establish a set of perfect evaluation system to evaluate the surrounding environment, management mode, subway equipment and facilities, etc. , to find out the conditions affecting the normal operation of the Metro power supply system in time, and take effective measures to solve these problems, improve the safety and stability of the Metro Operation System.