This paper aims to develop a new thermo-mechanical control process (TMCP) for micro metal forming, and as the first step to the goal, plastic deformation characteristics of crystal grains and its effects to microstructure changes in a shearing test of sheet iron are studied. Pure iron seat is used for a specimen, and an effect of shear deformation and subsequent annealing process on microstructure change is analyzed by using EBSD and microscope observation. It is found that drastic grain growth occurs in the single shear test when the applied shear stress was over 42 MPa. Although this stress was much lower than the apparent yield shear stress of the specimen, microscopic plastic deformation occurred in the grains and caused grain growth when the specimen was subjected to annealing. In case of the repeated shear test, drastic grain growth is not observed up to 44 MPa, which was greater than that of the single shear test. These results indicate possibility of precise TCMP by the micro metal forming.