Provided is a QoS providing method using a flow label in providing multimedia service in an IPv6 network and a system applying the same. According to the method, a signal connection server extracts session information from a communication request response signal transmitted from a destination in response to a communication request signal of a source, and transmits the extracted session information to a QoS provisioning server. The QoS provisioning server receives the session information, and generates a session key including flow label, and sets QOS information corresponding to the session key. The QoS provisioning server transmits the session key and the QoS information to an IPv6 node, and transmits QoS provisioning completion information to the signal connection server. When the signal connection server receives the QoS provisioning completion information, the signal connection server transmits the received communication request response signal to the source. The IPv6 node forwards an introduced packet on the basis of the transmitted session key and the QoS information.