Abstract: Dendritic cells (DCs) are unique specialized antigen-presenting cells capable of priming naive T cells and inducing antigen-specific cytotoxic T lymphocytes. There are increasing evidences that DCs constitute a complex system of cells that initiate and regulate immune responses， and result to two opposite outcomes：immunity or tolerance. In recent years， varieties of treatments for cancer patients have increased rapidly， tumor antigen pulsed dendritic cell-based vaccination as a immune therapy is treated to cancer patients. This paper describes some of the characters and functions of DCs， the mechanism of tolerance in cancer， and discusses the problems and perspectives for dendritic cell vaccines for cancer patients.