A method, a system, and a device for switching a service unit are provided. The method includes: determining a target service unit; and triggering the target service unit to publish first routing information according to configuration information of a first service unit for a first load balancing task, so as to replace the first service unit to provide a traffic distribution service for the first load balancing task. When the entire service network needs to perform disaster tolerance switching and capacity dispatching, the method provided in the embodiments of this application can effectively improve the real-time performance of traffic switching, and avoid the problem of relatively poor real-time performance of traffic switching caused by the influence of DNS cache in the existing technologies.