Recently, the power management becomes significantly important for the ultra power wireless sensor node powered by energy harvesting devices. In this paper, a power management system from battery to wireless sensor node is proposed for wireless structure health monitoring applications. By using the proposed circuits, the power supply of a sensor network node is switched on only when some event is detected to reduce its average power consumption. In the proposed circuit, the nanopower reference is utilized to bias control circuits. Therefore, the proposed management system has an extremely low power consumption of less than 100nA standby current. The proposed circuits are implemented with a 1.2μm CMOS process. Experimental results demonstrate the low power feature of the proposed power management system.