【Abstract】 Objective To review the research progress of possible mechanism of indoleamine 2, 3-dioxygenase(IDO) in immunological regulation and function of transplantation immunity. Methods The advances in the IDO location, immunological regulatory mechanism and function of transplantation immunity were introduced based on the recent related l iterature. Results IDO played an immunoregulatory role by locally depleting tryptophan in tissue microenvironment which resulted in immunosuppression of allogeneic T-cell prol iferation. IDO cDNA was del ivered to chromosome in interesting cells by gene transfection and stimulated to express, which was associated with a prolongation in allograft survival in vivo . Conc lu sion IDO offers a new way in transplantation immunity, and this provid novel method for elevating allograft survival rate.