A power-line carrier (PLC) terminal control apparatus, system, and method, where the PLC terminal control apparatus is configured to receive a subscription request sent by a PLC terminal system, where the subscription request includes an identifier of the PLC terminal system and a topic for controlling the PLC terminal system, establish a correspondence between the topic and the identifier of the PLC terminal system in a mapping table according to the subscription request, send a subscription response message to the PLC terminal system according to the correspondence, where the subscription response message includes the topic, receive a control message published by a message queuing telemetry transport (MQTT) publisher, where the control message includes a control word and the topic, and the control word controls an operation performed based on the topic, and send the control message to the PLC terminal system according to the correspondence.