As mobile devices of embedded systems prevail in our daily life, energy saving emerges as one very important issue and power management techniques are desirable. This paper presents the design and the implementation of a dynamic power management mechanism (DPMM) for embedded systems running micro-kernel operating systems. The DPMM is composed of policy manager, DVFS (Dynamic Voltage Frequency Scaling) controller, DPM (Dynamic Power Management) server, resource management flags, and DPM library. They are imple-mented to execute on an embedded system platform equipped with an XScale PXA270 processor and various I/O interfaces or devices running Zinix micro-kernel operating system. Testing results indicate that this DPMM effectively achieves power management in the system.