The present invention is suitable for the technical field of equipment data interfaces, and provides a USB device and a vehicle-mounted system. The USB device comprises a USB flash disk main body, wherein a USB interface is arranged at the front end of the USB flash disk main body; the USB flash disk main body comprises an MCU (Microcontroller Unit), a wireless communication module and a memory module, wherein the MCU is connected with the USB interface and has a USB OTG function, and the wireless communication module and the memory module are connected with the MCU having the USB OTG function. Through the USB device and the vehicle-mounted system, disclosed by the present invention, the problem that when a conventional vehicle-mounted device plays audio and video data, if the content in the USB device needs to update, the USB device needs to be converted into a data transmission mode, so that the problem play of the audio data is stopped, can be effectively solved.