The invention discloses a multimedia file sharing method and system used in a network. The system includes a first user device, a server and a second user device. The method includes the following steps. The first user device receives a multimedia data from a multimedia source, converts the multimedia data to the multimedia file and stores it. The first user device transmits information of the multimedia file including a characteristic of the multimedia file and an IP address of the first user device to the database of a server to be stored. When the second user device sends a file searching request and searches the database of the server, it obtains a file searching result including the information of the multimedia file and transmits the file searching result to the second user device. The second user device downloads the multimedia file from the first user device according to the information of the multimedia file.