Abstract: Real-time tasks scheduling is key problem in real-time system, real-time dynamic scheduling is main aspect of real-time scheduling. When real-time scheduling is used in practical system it may just use limited number of priority level. When real-time scheduling theory carry out theoretic analysis, all of them assume that there are unlimited number of priority level. The paper present the algorithm of dynamic real-time scheduling in the condition of limited priority level, and presents the minimum number of priority level that the tasks system schedules dynamically. Finally, the algorithm complexity is analyzed.