The invention discloses a prompting device for preventing the chassis of a motor vehicle from contacting the ground. The prompting device comprises a plurality of ultrasonic sensors, a processor and a prompting device, wherein the ultrasonic sensors are arranged at the front end of the vehicle; each ultrasonic sensor is arranged on a corresponding vertical slide rod through an elevating device, and is used for transmitting ultrasonic signals and receiving generated echo signals when the signals are hindered by a front barrier; the processor is arranged in the vehicle, is connected with the ultrasonic sensors, and is used for calculating the distance of the front barrier according to time for transmitting ultrasonic waves and receiving the echo signals; the prompting device is arranged in the vehicle, and comprises a sounding device and a display device which are connected with the processor; the sounding device is a horn; the display device consists of a plurality of light-emitting diodes of which the quantity corresponds to that of the ultrasonic sensors; and each light-emitting diode corresponds to one ultrasonic sensor. According to the prompting device, the distance of the barrier influencing the running of the vehicle can be measured in advance, so that a driver is prompted to avoid the barrier, the safety can be judged accurately in advance, and a scientific basis is provided for the driver.