Team with uncertain members and synchronous collaboration are two salient features among the many groupware-supported requirements in the business processes of electric power enterprise. Traditional workflow management systems have difficulties in supporting such features. Through extending ordinary workflow model in modeling method and groupware-supporting mechanism, we designed and implemented a groupware-supported workflow management system. Compared with traditional workflow modeling method, this method has more capabilities in describing groupware activities and makes modeling simpler. This paper introduces the modeling method for groupware activity and the mechanism supporting synchronous collaboration in our workflow management system. The applications of the system in electric power enterprise are also introduced.