The present invention provides a high-availability ID generator, and an ID generation method and device thereof. The high-availability ID generator comprises a master database and at least one slave database deployed in a distributed manner. The ID generation method comprises: when the master database runs normally, receiving an ID generation request and generating a unique auto-incremented ID; and after detecting a fault of the master database, performing active/standby switching between the master database and a normally-running slave database. In the present invention, the master database and the slave database can perform active/standby switching to generate an ID, thereby ensuring high availability.