The invention discloses a network service quality monitoring method, a sender and a relay device. The method comprises the following steps: the sender receives a first message of starting monitoring sent by a network manager; the sender determines identification information of a first relay device that needs to be monitored, wherein the first relay device is a relay device directly connected withthe sender; the sender responds to the first message, and sends a monitoring request message to the first relay device according to the identification information of the first relay device; the senderreceives a monitoring response message sent by the first relay device, wherein the monitoring response message is a response message of the monitoring request message; and the sender sends the monitoring response message to the network manager.