Abstract: In the passive infrared detection conditions, according to the dynamic target detection reliability and military defense needs, a dynamic/static double coordinate sensing system was put forward in this paper. Static sensing system was not only a standard -two -dimensional coordinate system, but also a benchmark of moving target detection; and moving coordinate sensing system was a cross coordinate system in the horizontal plane, swinging back and forth in the range of 90 at a constant angular speed. So the proposed system solved the problem of pyroelectric infrared sensor that perceived distance was inversely proportional to the angle of field contradictions, and it realized full range perception of battlefield. A theoretical model and mathematical model of perception system was presented. Verified by experiment, the theory, which has a certain practical value, is practicable, and the system established is reliable.