Abstract: In order to investigate a mechanism of infrasonic signals, we have developed a device, which can collect infrasonic sound wave automatically. The system can not only record graphs but also store data files. Programed by corresponding software, the recorded infrasonic signals can be analyzed and dealt with; therefore this system has altered the status which can only record single graphics. The paper has introduced the working elements, software and hardware scheme of the infrasonic observation system. Some abnormal infrasonic signals observed by this system are offered provided, and the methods of how to analyze, distinguish and classify the signals are also presented.