為增強實時操作系統的防危性，在分析現有調度機制的基礎上，探討了最大關鍵度優先的調度算法，該算法是一種混合型的優先級實時調度算法，由靜態優先級、動態子優先級和靜態子優先級3部分組成，綜合了固定優先級調度算法和動態優先級調度算法的優點，既可充分利用處理器資源，又能在發生瞬時過載時保證關鍵任務不受非關鍵任務的影響，從而增強了實時操作系統的防危性。

To buildup the safety of real time operating system, after status quo of existing scheduling mechanism analyzed, brought forward a kind of novel safety scheduling mechanism based on Maximum Criticality First (MCF). MCF is a hybrid priorities real time scheduling algorithm which consisting of three parts, the first two parts are the assignment of the importance and user priority, which is done statically, the second part is the assignment of the dynamic priority based on minimum laxity first scheduling algorithm. MCF synthesizes the strongpoint of the fixed priority scheduling algorithm and the dynamic priority scheduling algorithm. By this way, MCF not only takes full advantage of resources such as CPU, also make critical task not suffer from other non critical tasks at transient overload. The safety of real time operating system is improved with MCF.