·AIM: To investigate the characteristics and criterion of graft rejection in mice model. ·METHODS: C57BL/6 or BALB/c mice corneal grafts were grafted onto BALB/c hosts. Each group was divided into two subgroups according to the corneal opacity scores 12d after transplantation. The characteristics of opacity and neovascularization were observed. Mice of the 12 th , 50 th day after transplantation, the grafts biopsy of mice in allogeneic group 1, which opacity score exceed 3, were prepared for histological observation and those restore transparent were endothelial stained. ·RESULTS: There was no difference of corneal opacity score on the 7 th and 12 th day after operation; the histological results had no disparity between syngeneic group and allogeneic group. On the 12 th day after surgery, the turbidity curve was apparent in grafts with opacity score 【2. Mononuclear cells were shown in grafts with opacity score reached 3 in allogeneic group 1. Different rejection performance was observed in tissue sections on the 50 th day after surgery. ·CONCLUSION: Grafts, opacity score exceeds 3 from the 7 th to the 12 th day after operation could not be judged as a rejection. We should pay more attention to the variation of grafts opacity since 12d after corneal transplantation.·