▎ 摘　　要

Although it is important for the study of graphene, identifying and characterizing the number of graphene layers is challenging. In this paper, we calculate graphene's transmission. The result shows that the phase change is more sensitive than the intensity change when light passes through graphene in some THz frequencies. Based on this fact, a simple route is presented for identifying the single or few layers of graphene sheets by using terahertz phase contrast microscopy (TPCM). The route is fast, and easy to be carried out.