China Telecom NetCare service is a unified cloud network integrated monitoring platform. The system monitors client’s network device, cloud applications, virtual resources, VPN and Internet. It is developed by China Telecom to provide the monitoring management and analysis services of network layer, transmission layer and application layer for enterprises. It serves the government and enterprise customers of China Telecom, and has very strict requirements for availability of the system. The high availability of a system is influenced by hardware, network, operating system, database, middleware, application itself and other aspects. This study focuses on the application layer’s high availability of the NetCare system, and calculates the availability of the system with actual measurement and reasonable estimation of data. Finally, we come to a conclusion according to the paper: when the remote disaster recovery system is excluded or included, the whole system’s availability is 99.9978% and 99.45% respectively.