Abstract: A quality of service control system includes an input device, a processing unit and an output device. The input device receives a packet. The processing unit obtains an Internet Protocol (IP) version and adds at least one extension column in an undefined IP header, so as to generate a quality of service control packet. The output device transmits the quality of service control packet. Similarly, an input device receives the quality of service control packet and achieves the effect of transmitting the packet with higher priority, determining a transmission rate and keeping data accessed for a specific time according to a packet rate control parameter configuration in the quality of service control packet.