Abstract: Web service composition is a key issue in Web service research area. Service replacement refers to the problem of identifying a service that can replace another service in the context of a composition with a specified functionality, and the analysis of service replaceability is an important issue for supporting seamless service integration and collaboration. It is known that performing formal analyses to verify the consistency of the composition effect, before and after replacement, is helpful for service dynamic composition. Existing solutions to this problem rely on analyzing service replaceability of the service, according to both the consistency of operations and the operation sequence, but decrease the space of replaceable services. Consequently, the authors propose a determination method of service replaceability on service effect. They use colored Petri nets as formalism foundation modeling and specifying Web services and reasoning on behavioral features of Web services composition. The whole work is achieved by modelling the service behavior using colored Petri nets, defining the trigger condition and result as a behavior effect, introducing the concept of service behavior consistency, and listing the algorithms to implement the process. The theorem presented and proved illustrates that the analysis approach is very useful for correctly building and reliably executing the composing service after service replacement.