In this paper we design and implement a home surveillance system based on an embedded system with multiple ultrasonic sensor modules to enhance the system's reliability. Each ultrasonic sensor module includes a transmitter and a receiver, and the modules are placed in a line direction. Because the ultrasonic transmission will spread at a beam angle, we use multiple ultrasonic receivers to receive the ultrasonic transmission. If any intruder passes through the ultrasonic sensing area, the ultrasonic transmission will be blocked by the human body. As the receivers will not receive any transmission from the ultrasonic transmitter, the system will sense when someone is passing through the surveillance area. We use a Majority Voting Mechanism (MVM) for a group of sensors. If over half the sensors in a sensor group sense a signal blocking, the majority voting program starts the Web camera. The mathematical equation and the sensing experiment show that we improve the system's reliabilities.