A method, system and network entity for negotiating a session description protocol (SDP) version improve a negotiation process where two communication parties negotiate an SDP version supported by both applications. Especially when the H.248 protocol is applied, by extending of a property parameter, the negotiation process between a media gateway controller and a media gateway can be achieved easily. A method, system and network entity for obtaining information of an SDP version allow one communication party to obtain information of an SDP version supported by the other party from the other party. Especially when the H.248 protocol is applied, by extending the property parameter, the media gateway controller may obtain the information of the SDP version supported by the media gateway easily.