The present invention proposes a method for implementing a customized video service in IMS networks and a network element for controlling sessions between terminals, wherein a first terminal is calling a second terminal under the control of a first network element, and the second terminal has subscribed a customized video service provided by a second network element. The method comprises: the first network element transmits to the second network element a message of requesting for playing video to the first terminal which includes media information about the first terminal, after having known that the second terminal has the customized video service; the second network element transmits to the first network element an acknowledgement with information on the video to be played, if it determines that the first terminal supports the format of video to be played based on the media information about the first terminal; the first network element transmits to the second network element a message with information on the customized video service, and transmits to the first terminal a reply with the media information of video to be played after having received from the second network element a response with the media information of video to be played; and a media path is established between the first terminal and the second network element, thereby the video customized by the second terminal being played to the first terminal, and the call request sent by the first terminal while calling the second terminal is forwarded to the second terminal by the first network element.