The invention discloses a wide-area-information-based power grid system and a method for stability analysis and control of a power grid. The power grid system is composed of a Global positioning system (GPS), preposed sub stations and a main control station. The preposed sub stations consist of pre measuring units (PMU) and control sub stations (APMU). The system sends local information measured by the PMU to the APMUs by a wide area communication network; and the information is also gathered at the main control station and is used as the basis of stability analysis and emergency control. According to the invention, a new development opportunity is provided for real-time emergency control of the power system; a wrong judgment situation may occurring at the main station can be avoided effectively; and an actual operation situation of the system can be reflected accurately. The system is suitable for real-time prediction and control.