The system structure， key techniques and application areas of wide area measurement system（WAMS） and wide area control system（WACS） are reviewed and the concept of wide area monitoring， alerting and control system（WAMACS） is proposed. Application functions based on pure phasor measurement unit（PMU） data and data mining are discussed， as well as application functions based on the combination of PMU data and dynamic simulation based on mathematical models. The paper points out the bottleneck of WAMACS theory and applications. Potential solutions are also presented based on the analysis.