This work mainly studied the deterioration layer structure, crystal grain size, crystal lattice distortion of ground surface in two-dimensional ultrasonic vibration grinding nano-composite ceramics. The research indicated that under a certain grinding condition the ductile deformation layer on the ground surface of nano-composite ceramics in two-dimensional ultrasonic vibration grinding is formed by the ways of material powdering, crystal grain fragmentation, materials extrusion, the crystal grain pull-off and so on. The transition layer between the surface layer and the base body is plastic deformation layer by the primarily ways of crystal lattice distortion and the crystal boundary slipping. The removed material in brittleness fracture mode is extremely few. In this work, the structural model of deterioration layer on ground surface in two-dimensional ultrasonic grinding nano-composite ceramics is put forward. The microscopic deformation mechanism of nano materials is inner grain dislocation of inner-grain-structure strengthened phase. Its deformation coordination mechanism is the the grain-boundary sliding of matrix grain and the coordinated deformation of intercrystalline second-phase. The TEM and SEM observation discovers that the nano particles dispersed in grain boundary stops crack from expanding in nano materials, which causes the materials to appear in transcrystalline fracture behavior. And this fracture behavior gives materials favorable finished surface. The plastic deformation is the dominant removal mechanism of the nano materials in two-dimensional ultrasonic vibration grinding.