Method and device for smart power management of the sensor nodes within a wireless sensor network to achieve extremely low standby current and fast power-up time at the same time are provided. The method features a technique of centralized remote power-up scheme combined with local broadcasting power-up sequence to achieve fast power-up time and extended power-up coverage. It can manage the power-down sequence from a base-station to sensor nodes sequentially, while the power-up sequence broadcasts its power-up command from the base-station to all the sensor nodes within a sensor network. The device accepts same frequency band for both data communication and power-up message, and a RF switch separates receiving RF data and RF power-up message. The wireless power-up receiver is self-powered from power-up message and also generates power-up enable signal from it.