We propose a transforming method of MPEG-4 contents in order to present the contents on PDA devices in this paper. The method reconstructs the mp4 file according to transforming a scene tree in MPEG-4 contents when the contents are authored. The method reduces the size of each object in a scene of the content for presenting it efficiently on the small interface of a PDA device, and transforms visual objects in the scene into geometry objects in order to reduce initial loading time and a size of the contents. And an original object is presented on a PDA device when the user clicks the substituted geometry object. The method was applied to a conventional authoring tool, so we could find that the method showed an efficient presentation of the contents on a PDA device.