n the basis of summarizing the modles of 2D grain rearrangement in superplastic deformation, 3D grain rearrangement in superplastic deformation has been investigated.Metallographic observations show that fine marginal lay'Cr grains at latitudinal direction ofplate specimens of 1#(8090)Al-Li alloy filled in the cavities created at tension direction oflarge central layer grains, and completed grain rearrangement. Grain emergence and rotation of large Al,Zr phase in Al-Li-Zr alloy deformed were observed With SEM.The results show that fine grains fill 'in f cavities by grain rotation, which is a process of energy decrease. Thephenomena of decrease in the latitudinal size of specimen and migration of local necking atthe specimen margin in the superplastic deformation ean be explained by the motion of finegrains at latitudinal direction.