With the availability of cheap and small micro sensor nodes，wireless sensor networks(WSN)foresee awide range of applications．Sensor operating systems for ease of development for WSN applications are essentiallyneeded．This paper introduces the SenSpire operating system especially designed for wireless sensor networks．Theexecution model iS precisely designed to provide real—time ability while maintain the effectiveness to the greatest extent．The concept of software interrupt masking，bottom half and realtime task scheduling based on the event-driv—en model are introduced．The memory subsystem adopts a static allocation and dynamic management scheme．Staticanalysis for task set and static memory allocation improve the predictability of the system．At the sanle time。the hierarchical scheduling policy and dynamic memory management scheme provide a flexible software deployment environrnent for sensor nodes．