Abstract: Based on the introduction of the development of the international SBAS, this paper analyzes the development and service performance of MSAS. It is found that the service area of MSAS can cover the eastern region of China. After describing the MSAS message type and the calculation method of civil aviation user positioning and protection level, the actual service performance in the eastern region of China is evaluated through the actual flight test. The evaluation results show that in eastern China, the positioning accuracy of MSAS is better than that of LPV-250 (16 m horizontally and 20 m vertically); NPA availability and continuity reach 100%; the user protection level meets the integrity requirements. MSAS has effective enhanced positioning and integrity-assurancing capability in eastern China, so that relevant users in the region can use the service according to their own needs; at the same time, MSAS has realized the expansion of service area based on its limited local monitoring stations, which also provides a reference for the expansion of BDSBAS service area and the improvement of service performance in China.