Provided are a method and device for sending media data. The method is realized by providing a media substitute node between a sender and a receiver. The method comprises: a media substitute node receives an original media data stream from a sender; the media substitute node acquires substitute data for substituting for the original media data stream within a designated interval; the media substitute node converts the format of the acquired substitute data into a media format which conforms to a media parameter of the original media data stream; and the media substitute node sends the converted substitute data to the receiver within the designated interval. The technical solution provided in the disclosure is adopted to solve the technical problems in the related art, such as the reduction in communication efficiency due to the need for re-negotiating a media parameter between substitute data and original media data.