A new structure that can decrease the crosstalk of planar HgCdTe(MCT) Focal Plane Arrays(FPA) was investigated theoretically.In order to improve the property of FPA,the geometry of the FPA's substrate was designed to increase the spectral response and to decrease the crosstalk.The method of structural optimization was established.The two-dimensional simulation of Hg_(0.78)Cd_(0.22)Te devices was performed by using a device simulator.The results of calculation indicate that the spectral response increases 9.6%,and that the crosstalk decreases down to 1.05% from 5.23% when minority carrier lifetime is 10ns.