Transaction processing, as the key technology of web service composition (WSC), has obtained wildly concern. WS-BPEL[1] as a primary web service composition description language, which couldn’t coordinate these web service transactions that distribute in a distributed computing environment reach consistent agreement on the outcome. This paper proposed two kinds of transaction types and coordination mechanisms by analyzing the features of WSC transaction, and a transaction processing coordination model based on BPEL was lastly proposed, by which extending the structure of BPEL firstly and then introduced the coordination mechanism into it. The model was validated by an instance at last.