The SOAP protocol is the de facto communication standard for Web services, providing extensibility, simplicity, robustness and especially interoperability. However, the performance of SOAP is relatively poor, mainly because SOAP needs extra process parsing and building message to process an XML document. Therefore, performance improvement for SOAP-based communication system is a challenge to apply Web Services to high-performance systems. This paper proposes the "double-channel communication" approach, by allowing establishment of a second communication channel between Web Services, to facilitate the application of Web Services in systems that require bulk data to be transmitted efficiently. Then experimental tests highlight the performance improvement that the double-channel communication approach makes in communication efficiency.