With the development of laser technology, laser can be applied to various fields. With the aim of studying laser application in monitoring, a set of audio monitoring and positioning system was designed and produced using photoelectric detection principle. The system will be placed in outdoor about 10 meters far away from the goal, two parallel lasers will be lased to the window. And the reflection of the light spot will be detected by system composed of two sensors. As the spread of indoor sound meets glass, the glass will cause tiny mechanical vibration, making the light spot in the silicon photocell occur tiny displacement. Through the acquisition of the photocurrent signal change, the indoor sound signal content will be reduced to the monitor. The result of the experiment was satisfactory.