A transient-triggered DC voltage-sustained power-rail ESD clamp circuit comprises: a transient-triggered module, a DC voltage-triggered module and a discharge device, wherein the transient-triggered module is connected with the DC voltage-triggered module and the discharge device respectively. When an ESD event is approaching, the ESD protection circuit can be turned on well and quickly, and can effectively avoid the problems of erroneous triggering and latching-up caused by quick power-on and high-frequency noise at the same time.