Along with the extending application of uncooled infrared focal panel arrays, the requirements for high quality infrared imaging are increasing continuously. The nonuniformity correction technology based on existing unary linear theoretical model has become the bottleneck of infrared imaging quality improvement. Through theoretical analysis of un-cooled infrared focal panel array photoelectric response mechanism and its imaging process, the primary influencing factors for infrared sensor response and their nonuniformity are deduced in this paper. A theoretical model of binary nonlinear nonuniformity for uncooled infrared focal panel arrays is present. The impact of surrounding temperature on sensor response is taken into account in this model. Experimental test results are given in this paper. Statistic analysis results show that this model can give reasonable prediction of the responsive curve for uncooled infrared focal panel arrays sensor in wider scene radiation and surrounding temperature range. This model describes the exact photoelectric response relationship between infrared radiation and infrared detector output signal. Furthermore, this model reflects influencing factors of nonuniformity for infrared imaging more accurate than the existing unary linear theoretical model.