The present invention provides a power adjustment method, a network management system, a CMTS, and a CM. The power adjustment method includes: obtaining, by a network management system, a first SNRCM between two CMs connected to a CMTS, where the first SNRCM represents a signal ratio of a signal sent by the CMTS to a first CM and received by the first CM to a signal sent by a second CM to the CMTS and received by the first CM; and sending, by the network management system, indication information to the CMTS based on the first SNRCM, and a first relationship between an SNRCM and a transmit power at which the CMTS sends a signal to the CM.