The increasing complexity of software systems in embedded systems or industrial business domains has led to the importance of reliability analysis for current systems. Reliability analysis has become a crucial part of the system development life cycle, and a new approach is needed to enable an early analysis for reliability estimation, especially for the system under design. However, the existing approach neglects the correlation between system resource and system task for estimating system reliability. This subsequently restricts accuracy of the estimation as well as causing difficulties in identifying critical resources and tasks during the design phase. This paper proposes a model-driven system reliability estimation using a scenario-based approach to estimate system reliability and identify its critical resources and system tasks during the design phase. This model is based on the PerFAM model, which can specifically view timing failures through a system scenario. The proposed approach is validated by the application of a sensitivity analysis into one case study. The case study demonstrates an essential relationship between system reliability, as well as both resources and tasks, which ultimately becomes the integral part for a system reliability estimation assessment.