A data transmission device includes a TypeC interface, a wireless module, a first data transformation chip and a microprocessor, wherein the TypeC interface is connected with the first data transformation chip, the first data transformation chip is connected with the TypeC interface and the microprocessor, and the microprocessor is connected with the wireless module. When the TypeC interface of the data transmission device is inserted into a user's terminal device, the data transmission device automatically obtains media data presented on the screen of the terminal device, and transmits the media data being converted and compressed, using the wireless module, to a data receiving device for presentation of the media data.