Service choreography has become an emerging and promising technology to design and build complex cross-enterprise business applications. Dynamic composition of services on the fly requires mechanisms for ensuring that the component services in the composition are compatible with each other. Current service composition languages provide notations for describing the interactions among component services. However, they focus only on the compatibility at the syntax and semantic level in an informal way, yet ignoring the dynamic behavior within services. This paper emphasizes the importance of the behavior in the compatibility verification between services and utilizes the -calculus to model the service behavior and the interaction in a formal way. Based on the formalization, it proposes a method based on the operational semantics of the -calculus to automate the verification of compatibility between two services and presents an algorithm to measure the compatibility degree quantitatively.