Calcineurin(CaN), a Ca²⁺/calmodulin-dependent protein serine/threonine phosphatase, broadly distrbutes in various mammalian cells and involve into regulation of cellular function. It was known that CaN play a central role in T cell activation and is essential to transmitter release and synapic plasty. It is reported recently that CaN is likely a link of Ca²⁺ signal with cardiac hypertrophy. The advances in the molecular structure, enzymatic propertied, distribution and biological function of CaN were summrized.