The multi-task priority allocation method of a real-time embedded uni-processor system is studied.Firstly, the Deadline Monotonic (DM) priority allocation method is selected and implemented for the multiple tasks, which are classified for running the acquisition and incentive software of the avionic relay system.Then, by using the preemptive priority-scheduling algorithm of VxWorks, the schedulability of the task set is theoretically analyzed and calculated.The general process of the scheduling design for the VxWorks-based data acquisition and incentive software is also given.Finally, a data-forwarding experiment was performed on the avionic relay system based on the scheduling algorithm.The experimental results show that the maximum delay time for the avionic relay system to forward data does not exceed 3.5 ms, which can realize the stable and correct forwarding of 4 types of data.Therefore, the avionic-relay task scheduling design based on the preemptive scheduling algorithm of DM priority allocation can meet the real-time and reliability requirements.