We analysed the high resolution lattice image of interface between crystalline region and amorphous region produced by ion implantation in GaAs with optical diffra-ctometer. The preliminary results show the structure variation at the interface. There are five districts from amorphous to crystalline region. They are: amcrphous area; nuclei, crystallite and low dimensional ordered area; polycrystalline area; distorted mo-nocrystalline area; and monocrystalline area.