Abstract: Crosstalk is one of the important parameters for InfraRed Focal Plane Array (IRFPA) performance evaluation. As the size of IRFPA element reduces, the size of testing spot of traditional small spot test method is close to or even greater than that of IRFPA element, wherein new theory and method for crosstalk measurement is required. First, typical situations are analyzed when infrared spot illuminates onto IRFPA. Then the electrical signals of adjacent IRFPA elements are studied, and new crosstalk model for small element IRFPA is proposed based on 8 neighboring elements. 4 neighboring elements and traditional situation are two special cases of crosstalk model based on 8 neighboring elements. Mathematical analysis shows: the size of testing spot affects crosstalk apparently in small element IRFPA; crosstalk model based on neighboring elements can realize small element IRFPA crosstalk measurement using existing equipment, given that the software is modified.