An ultrasonic positioning system is introduced in this paper. With the help of the system the blind can get early warning of where the obstacle is. The system has three ultrasonic sensors and an ultrasonic emitter. The sensors are located at different apexes of a right triangle. The ultrasonic emitter is arranged at the right angle of the right triangle. This paper discusses two different device position arrangements and their positioning deviations for the same positioning system. An area of ±15°, 1 meter to 2 meters in front of the sensors is used as a test area for the two different arrangements. Some simulation results and conclusions are also given in this paper.