The invention discloses an unmanned plane data relay device based on a mobile data network and a method thereof. The unmanned plane data relay device comprises an airborne radio, multiple mobile base stations, a data relay server, and a ground station computer for sending an instruction, wherein each mobile base station comprises a base station radio for receiving the data sent by the airborne radio and sending a control instruction from the ground station computer, a mobile wireless data network card, a base station computer, and a data acquiring unit installed in a base station computer; the base station and the airborne radio are in wireless communication; the base station computer is respectively connected with the mobile wireless data network card and the base station radio; the data acquiring unit is used for connecting the base station computer to the internet through the mobile data wireless network card; the data relay server is connected with the mobile base station, and comprises a relay program module; the relay program module is in wireless connection with the mobile wireless data network card; a client program module is installed in the ground station computer; and the ground station computer is connected with the data relay server.