The invention discloses an instantaneous impact pressure pulsation sensor and a measuring method thereof. The sensor comprises a capillary, a lateral flush pipe, a water storage cavity, a water guide pipe, a pressure stabilizing cavity and a pressure sensor unit; the capillary and the pressure stabilizing cavity are arranged between the pressure sensor unit and a pressure measuring point, and the water column in the capillary can be used as a damping section for damping instantaneous pressure impact, so that the measurement precision can be ensured and the instantaneous pressure impact can be borne when the conventional pressure sensor unit is used for pressure test; besides, the lateral flush pipe, the water storage cavity and the water guide pipe are arranged on the side wall of the pressure stabilizing cavity, and the capillary can be flushed with water to flush away bubbles inside the capillary, so that bubbles are prevented from entering the capillary in the measuring process, and a better impact damping effect is achieved.