With the development of computer and embedded technology, ubiquitous computing age is coming. In the ubiquitous age, people could get all kinds of services anywhere and at any time. In this paper, we design an indoor location system based on ultrasonic sensor and radio frequency technology. The ultrasonic positioning technology has many merits of high positioning accuracy, simple circuit structure and low cost. There are some components such as locating system, communication system, location system, security system and so on, emphasized supporting technologies in order to provide researchers with general cognition. The principle and the design of the system are described in detail. The system consists of the single chip circuit, the circuit of ultrasonic, the circuit of radio frequency signal, communication interface circuit and so on. Perceptual system can promote environmental intelligence and human services development, but also can promote public places security monitoring and early warning intelligence and automation.