With the continuous development of cloud computing technology, a variety of cloud computing platforms are gradually mature. The open source cloud platform OpenStack has also gained the major IT giant's attention and support, which develops rapidly. This paper discusses the system architecture of the OpenStack cloud platform and the system's high availability, and focuses on the two modes of achieving high availability of the system: Active/Passive, Active/ Active. And the implementation of the high availability of OpenStack is analyzed, providing a basis for improving the availability in the construction of the OpenStack cloud platform.