The　emergence　of　many　heterogeneous　sensor　systems　on　the　Web　has　produced　huge　amounts　of　sensor　data.　This　requires　building　the　customized　and　automated　processing　methods,　which　can　be　formed　by　connecting　the　services　on　the　Web.　Based　on　the　semantic　Web　services　markup　language　named　OWL-S,　the　algorithms　for　processing　sensor　data　on　the　Web　are　represented　as　the　service　ontologies　and　become　the　machine-readable　models.　In　this　paper,　the　composite　service　for　fusing　the　sensor　data　of　vibrating　wire　strain　sensor　is　organized　based　the　atomic　services　on　the　Web.　At　last　the　service　is　formally　represented　as　Pi-Calculus　and　verified　by　the　software　tool　MWB.