A dynamic time window and cache method under the heterogeneous network transmission is provided, including adding Available_Time and Asset_Size attributes of the media content in the signaling or other places for the existing signaling at a MMT, so that the client terminal gets the time when the corresponding media content is available and the size of the media content; at the same time determining the network bandwidth and the network delay of the content from the broadband to the client under the current broadband network by the client; wherein the client terminal calculates the time interval for transmitting a request for caching in advance and the size of a cache window required by the terminal through the available time of the content of a broadband source and the delay of a broadband channel.