A method for numbering working services on a channel protection ring. The process of numbering working services includes: after detecting that the node has an added or dropped working service in the downstream segment in the specified direction, the node on the ring sends a notification message which includes the identifier corresponding to the node to the downstream node in the specified direction; after receiving the notification message and detecting that the node has an added or dropped working service in the downstream segment in the reverse direction of the specified direction, the node on the ring assigns a serial number to the working service according to the identifier in the notification message. The present invention enables automatic numbering of services and dynamic adjustment of the service numbers on the ODUk protection ring, and fulfills the requirements of ODUk protection switching.