A power adjustment method, comprising: obtaining, by a network management system, a first co-channel mutual interference signal-to-noise ratio SNR CM between two cable modems, CMs, connected to a cable modem termination system, CMTS, wherein the first SNR CM 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; characterized by further comprising: obtaining, by the network management system, a first co-channel self-interference cancellation capability signal-to-noise ratio SNR CMTS of the CMTS, wherein the first SNR CMTS represents a signal ratio of a signal sent by the second CM and received by the CMTS to a signal that remains after self-interference cancellation is performed on a signal that is received by the CMTS and sent by the CMTS to the first CM; and sending, by the network management system, indication information to the CMTS based on the first SNR CM, a first relationship between an SNR CM and a transmit power at which the CMTS sends a signal to the CM, the first SNR CMTS, and a second relationship between an SNR CMTS and the transmit power, wherein the indication information is used to instruct the CMTS to adjust a transmit power at which the CMTS sends the signal to the first CM, so that an SNR CM corresponding to the adjusted transmit power is a target value of a co-channel mutual interference signal-to-noise ratio between the two CMs and an SNR CMTS corresponding to the adjusted transmit power is greater than or equal to a co-channel self-interference cancellation capability signal-to-noise ratio threshold, the co-channel mutual interference SNR between the CMs is determined based on a CM group. obtaining, by a network management system, a first co-channel mutual interference signal-to-noise ratio SNR CM between two cable modems, CMs, connected to a cable modem termination system, CMTS, wherein the first SNR CM 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; characterized by further comprising: obtaining, by the network management system, a first co-channel self-interference cancellation capability signal-to-noise ratio SNR CMTS of the CMTS, wherein the first SNR CMTS represents a signal ratio of a signal sent by the second CM and received by the CMTS to a signal that remains after self-interference cancellation is performed on a signal that is received by the CMTS and sent by the CMTS to the first CM; and sending, by the network management system, indication information to the CMTS based on the first SNR CM, a first relationship between an SNR CM and a transmit power at which the CMTS sends a signal to the CM, the first SNR CMTS, and a second relationship between an SNR CMTS and the transmit power, wherein the indication information is used to instruct the CMTS to adjust a transmit power at which the CMTS sends the signal to the first CM, so that an SNR CM corresponding to the adjusted transmit power is a target value of a co-channel mutual interference signal-to-noise ratio between the two CMs and an SNR CMTS corresponding to the adjusted transmit power is greater than or equal to a co-channel self-interference cancellation capability signal-to-noise ratio threshold, the co-channel mutual interference SNR between the CMs is determined based on a CM group. obtaining, by the network management system, a first co-channel self-interference cancellation capability signal-to-noise ratio SNR CMTS of the CMTS, wherein the first SNR CMTS represents a signal ratio of a signal sent by the second CM and received by the CMTS to a signal that remains after self-interference cancellation is performed on a signal that is received by the CMTS and sent by the CMTS to the first CM; and sending, by the network management system, indication information to the CMTS based on the first SNR CM, a first relationship between an SNR CM and a transmit power at which the CMTS sends a signal to the CM, the first SNR CMTS, and a second relationship between an SNR CMTS and the transmit power, wherein the indication information is used to instruct the CMTS to adjust a transmit power at which the CMTS sends the signal to the first CM, so that an SNR CM corresponding to the adjusted transmit power is a target value of a co-channel mutual interference signal-to-noise ratio between the two CMs and an SNR CMTS corresponding to the adjusted transmit power is greater than or equal to a co-channel self-interference cancellation capability signal-to-noise ratio threshold, the co-channel mutual interference SNR between the CMs is determined based on a CM group.