A conserved family of aspartate-specific cysteinyl protease(Caspase) has been identified as mediators and excutors of programmed cell death (PCD) in mammalian cell. Proapoptotic signals culminate in activation of different initiator caspase which，in turn，activate effector caspase through enzyme cascade pathways. Active effectors cleave a set of substrates and result in cellular disassembly. Caspase family is the critical elements in PCD. They regulate cell death or survival by interaction with many proteins(activators or inhibitors).