Abstract: The hybrid mechanism combining contention-based and schedule-based ways is an important solution for MAC protocols of wireless sensor networks (WSN). μ-MAC is an effective hybrid MAC protocol of WSN. After a deep investigation of μ-MAC, an adaptive hybrid MAC protocol Aμ-MAC is proposed for the dynamic-traffic data collection applications. It solves the problems of the adaptability to dynamic topology and clock synchronization in μ-MAC, and further supports better adaptability to load traffic. The simulation results show that Aμ-MAC can enhance the expansibility and adaptability of the protocol and enable better network survivability, and yet has almost the same energy-efficiency and latency as μ-MAC.