Software reliability is one of the most important quality indices in software quality evaluation. Reliability analysis based on software architecture has become a researching hotspot. This paper makes a review on existed architecture-based reliability evaluation models, and puts forward the shortage of these models. As petri net has a good ability of description for concurrency and asynchronism, this paper focuses on the research of petri net model. Transitions are divided into time transitions and instantaneous transitions. Time-related reliability, including time-delay reliability and temporal reliability, are added. Then the reachable state transition matrix is set up and system reliability evaluation proceeds. The method above is used into a avionics embedded software. At last we accomplish the architecture modeling, reliability evaluation, proving the effectiveness and feasibility of this method.