The tensile samples of different grain sizes were obtained by heating 0. 1,0. 2,0. 4,0. 6,0. 8 and 1. 0mm T2 copper at 450,650 and 850 ℃.Then,the deformation of the samples in uniaxial tension tests was measured by the digital image correlation (DIC) method,and the relationships between the relevant parameters (namely,the yield strength,the tensile strength,the maximum uniform strain and the fracture strain) and the grain size as well as the sheet thickness are evaluated.Experimental results show that the mechanical properties of the annealed T2 copper sheet show an obvious size effect; specifically,the tensile strength,the maximum uniform strain and the fracture strain decrease with the decrease of the sheet thickness or the increase of the grain size,and they all have an approximate exponential relationship with the ratio of the sheet thickness to the grain size.