This paper is motivated by the challenge to traditional development process of embedded systems from the evolution of dependability requirements, which leads to manual analysis and revision of system designs at design-time or post-implementation at a high cost, especially when the target system is complex or large. This paper proposes a complementary methodology, namely the model monitoring approach, to fill in the gap between the evolution of dependability requirements and traditional development process. The novel approach models functional and dependability requirements separately, and contains two alternative implementation techniques: model monitoring and model generating. The paper illustrates the methodology with examples and comparison with the model checking approach, to show better support of the evolution throughout the life-cycle at a lower cost.