Four element cross array static perceptual system,which is consisted of four Fresnel lens and four pyroelectric sensors,has detection viewing field with a large angle and adjacent overlapping sensing area,which leads to low detecting precision of the traditional perception system coordinate. An improved two dimensional coordinate system is proposed to enhance the reliability of target detection. The cross coordinate system is rebuilt by the overlapping parts of adjacent sensing region. A theoretical model of the new coordinate system is established in this paper. The experimental result shows that the design of this improved coordinate system is practical and reasonable,and the target detection accuracy is improved. The new coordinate system has a certain actual application value.