Abstract: Currently the TinyOS task scheduling is based on first comcfirst-served non-preempting strategy, which is not able to give emergency tasks quick response, and throughput of nodes is lower. To address this issue, this paper proposed a preempting algorithm, HRRF ( Highest Response-Ratio First) Algorithm. Through executing real-time tasks within an higher priority, it met system requirement for the real-time response, and improved processor' s response speed. Through executing soft real-time tasks based on Highest Response-Ratio (waited time/run time) scheduling priority strategy,system throughput was increased. The TinyOS test result indicated that under the condition of not affer ting (decreasing) the original performance, HRRF strategy greatly improved sensor network performance in working on real-time tasks.

Key words: TinyOS, HRRF algorithm, Preemptive scheduling, Real-time