The receptive field (RF) theory and the lateral inhibition (LI) mechanism are of the same view.According to the eye′s microsaccade phenomena supported by the medicine field, the proposed opinion states that image spot of object will project the On center RF and off center RF alternatively in the split seconds, so a new vision mechanism′s assume based on this opinion is proposed; this paper discussed the property of Off center RF in detail, and put forward a mathematic model that has a advantage to carry out the edge detecting algorithm, especially to the military IR image, this algorithm posses the characteristics of speeding and feature magnify.