The present invention relates to a method for obtaining Quality of Service (QoS) information of a session. The present invention may obtain QoS information of a session by analyzing a control message of the session on a Media Proxy (MP). The present invention may also make a QoS analysis only on the session which needs the QoS analysis, according to configured policy information, and returns the corresponding QoS analysis result to a Signaling Proxy (SP) or another particular server. Moreover, for the session on which the QoS analysis needs to be made, it may be configured that the QoS analysis is to be made on only parts of the control messages. Therefore, the implementation of the present invention may not only save processing resources of the MP but also increase the efficiency of the QoS analysis for the session during the QoS analyzing and processing procedure.