In this paper, we present a systematic approach to translating BPML(Business Process Modeling Language) into the ${pi}-Calculus$. BPML is an executable business process modeling language, like BPEL4WS(Business Process Execution Language for Web Services). It is difficult to find a systematic approach to formalizing these languages; but, by formalizing them, the behavior of the processes can be analyzed and compared so that optimal processes can be designed. For this formalization, we analyzed the activity types and contexts of BPML and suggested the definitions of semantics for each type and context by using the ${pi}-Calculus$. In addition, we have shown the usefulness of our formalization scheme in that a typical order fulfillment process represented in BPML can be translated into the ${pi}-Calculus$.