The parameters in these software reliability models are usually directly obtained from the field failure data. Due to the dynamic properties of the system and the insufficiency of the failure data, the accurate values of the parameters are hard to determine. Therefore, the sensitivity analysis is often used in this stage to deal with this problem. Sensitivity analysis provides a way to analyzing the impact of the different parameters. In order to assess the reliability of a component-based software, we propose a new approach to analyzing the reliability of the system, based on the reliabilities of the individual components and the architecture of the system. Furthermore, we present the sensitivity analysis on the reliability of a component-based software in order to determine which of the components affects the reliability of the system most. Finally, three general examples are evaluated to validate and show the effectiveness of the proposed approach.