Based on finite difference time domain method (FDTD) and finite element method (FEM), the mechanism of Pt/CdS and InSb ultraviolet-infrared dual-color focal-plane arrays was investigated. It was found that a high ultraviolet photo response can be achieved for Pt/CdS Schottky junction under an ultrathin Pt top contact. Further simulations show that the ultrathin top contact can efficiently couple the infrared radiation for the dual-color focal-plane array detector. The center to center spacing of each pixel of 50 μm in the ultraviolet and infrared dual-color focal-plane array detector based on Pt/CdS and InSb junctions can significantly reduce crosstalk. Our work provides fundamental guidance for optimization and design of ultraviolet and infrared dual-color detector.