With the development of economy and the speeding up of our life, the number of cars in China is increasing year by year, which followed by the traffic accidents. In order to avoid the occurrence of traffic accidents, an ultrasonic proximity alarm device was designed in this paper. This system take MSP430G2553, a 16 bit controller of TI, as the controller. The ultrasonic transmitting circuit was formed by 74LS04 and MAX232. CX20106A was the core component of the ultrasonic receiving circuit. The measuring range of this device was between 17 cm~8 m, which is accurate and reliable. This system could be used on not only cars, but also the crane arm and guide apparatus, which can guarantee our safety.