This paper thus presents an electric power monitoring and management system based on the wireless sensor network (WSN). This system utilizes ADE7755 for electric power measurement, ATmega 48 as the microcontroller (MCU) and Texas Instruments (TI)'s CC1100 for real-time wireless data communication. Moreover, a master-slave polling wireless protocol with trunk relay function is designed to achieve more efficient in functionality. Furthermore, the monitoring node can measure multiple electric parameters including current and voltage besides electric power. This system is cheap, easy to implement, low cost and reliable so it could be applied in the electric power management of residential communities, schools, plants, and street lights.