Embodiments of the present invention provide a method for ensuring quality of service of an Internet Protocol television live broadcast service, and the method includes: detecting a live broadcast packet received from an original multicast group (100); if detecting that the live broadcast packet has an error or a loss, joining a multicast group corresponding to a delay multicast stream sent by a retransmission server, and receiving a delay retransmission packet from the delay multicast stream (102); and recovering the live broadcast packet according to the received delay retransmission packet (104). Correspondingly, a terminal and a retransmission server are provided. Once the terminal detects that the original packet has a loss or an error, the terminal directly receives a packet from a delay packet stream sent by the retransmission server for recovering, thereby avoiding a NACK storm, simplifying the processing of the retransmission server, and improving the retransmission efficiency.