Aggregating components into software is a perfect approach to construct software with the maturity of component market. How to analyze software reliability from the reliabilities of its components and architecture should be answered. However, software in most of the proposed reliability analysis methods is static, while software development is a dynamic process, especially for component-based software, where pervasive process is iterative and incremental. Based on function abstractions, this paper presents a general model - component probability transition diagram, which is compatible with different kinds of components and enables reliability tracing through component-based software process.