Granzymes play a central role in cytotoxic T lymphocyte and natural killer cell-mediated apoptosis of target cell. Multiple granzymes are found in effector cells, and their mechanisms to lead to apoptosis are different. Effector cells kill target cells via multiple pathways. At least three pathways of apoptosis mediated by granzymes have been found. Moreover, the abnormal activity of granzymes is related to many human diseases, such as autoimmune diseases. Granzymes play an important role in inflammatory response in vivo. The biological features and mechanisms of granzyme A, B, C, K, and M to induce cellular apoptosis are summarized.