Garbage collection is a key part in the Java Operating System(JavaOS),which affects the efficiency of the whole system directly. Most garbage collection algorithms used in modern Java OS are derived from those used in the application level. The optimizing methods applied in the application level are Java Virtual Machine(JavaVM) oriented. But compared to JavaVM, JavaOS has higher privilege and more convenient strategy of managing resources. How to use these conveniences to improve garbage collection becomes a challenge that never faced the previous garbage collection algorithm designers. This paper analyzes the characteristics of memory management and garbage collection at the OS level. Then, based on the JUnicorn Java OS platform, using the conveniences provided by the OS platform, this paper designs and implements a high performance OS level garbage collection algorithm FLSP. The testing results show that working under this algorithm, system performance gains a 1.3 speedup on average. Meanwhile, it cuts off the average garbage collection pause time by 50%.