提出了以实时多任务系统中的任务链为组件，任务链运行时间比例作为组件的权重系数，建立实时多任务软件的可靠性建模方法。该方法符合实时多任务系统应用软件运行的实时情况，拓展了实时系统可靠性建模的思路，其可靠性模型可以给出单个任务链的可靠性参数，且建模方法还可以根据不同任务链的重要程度，进行可靠性分配并决定软件测试和投放时间。关 键 词 实时系统; 多任务; 任务链; 可靠性模型Abstract Taking lansaction as component in real-time multi-task system, and executeing time rate as the quotiety of lansaction, the paper present a method of reliability modeling based on lansaction for real-time multi-task software. The method tally with the actual situation of programm executing of real-time multi-task. The model can submit evaluation results of single lansaction, so, the reliability modeling is convenient for reliability assigning and determine test time according to importance of the lansaction.Key words real-time system; multitasking; lansaction; reliability modeling