The detection of human motion is widely used in the interaction of humancomputer, intelligent security, military intelligence and other fields. In this paper, an experiment platform is set up to gather and analyze the output signals of sensor with the design of signal conditioning and acquisition circuit by making use of the feature of the pyroelectric infrared sensor sensitive to the infrared radiation of human body. In the time and frequency domains, the motion feature extraction algorithm is designed to realize the detection of human motion patterns. The whole design process is introduced by taking the process of step jump extraction as an example. The proposed detection method has the advantages of low cost, high antiinterference ability, which has important value for the researching of the human detection.