The concept of Software Architecture (SA) provides a new way for the transition from the construct and requirement to implementation. Software architecture style is a classification of SA. Different style has different system characteristic. Through the research of software architecture style, we can direct the software development well using SA. Formalizing software architecture style made the communication more precise and convenient at the level of SA. Formalizing software architecture style will be beneficial to formal verification and comparison of different style. This paper proposes the service oriented software architecture style, formalizes the new service oriented SA style using formal specification notation Z, gives the definition of match and composition of service component, analyses the replacement of SA style and proves four theorems of replacement.