To reuse the information resource in the plant and respond to the frequent changes of the bidding rules， a plant bidding system is established based on the service oriented architecture（SOA） and business process execution language（BPEL） for Web services. The layer architecture and the deployment structure of the system and the business process management framework are presented. The ActiveVOS Designer is applied to model the bidding process in day-ahead market. Furthermore， the business process modeling is used into the BPEL server for choreographing and publishing the services successfully.