In this paper, we present a multi-agent system MAGS for the e-business processes monitoring in a web-based environment. We classify the types of agents in MAGS by their monitoring capabilities. An algorithm is given to the mechanism of supervising and controlling the execution of business processes. We then propose an abstract model of alerts, which can give warnings of infringement on business policies. The access control can also be realized by MAGS, which manifests in delivering different view of the business process to different roles participating in it. MAGS is successfully adopted in a customer service management system and proven flexible and practical.