In terms of the accumulation of historical data of the power system, China's power grids have accumulated a great number of dispatching and operating data which contains different voltage levels. Online safety and stability analysis conduct a comprehensive system assessment every 15 minutes, including power flow, short circuit, static safety analysis, voltage stability, transient stability, small disturbance stability, limit transmission power, and scheduling assistance decision-making, and the calculation data and result data are about 1G. Based on the six-month online historical data accumulated by a provincial power grid, this paper studies the characteristics of the actual power grid security and stability, and proposes a system stability analysis method based on the online security analysis of historical resources. At the same time, Considering the time-varying characteristics of the power system, an operation rule extracting method was proposed. Firstly, based on the correlation analysis methods, the corresponding features are selected for each type on the hierarchical grid. Then, a power grid security risk assessment system is established based on load ratio, and line limitation. Finally, this article automatically discovers the characteristics and rules of grid dispatching operations from numerous online data, provides a theoretical basis for operational mode and scheduling decisions, further improves the ability of large-scale grid dispatching and online safety analysis, and enhances the ability of power grids to resist the influence of external factors on safe and stable operations ability and has important practical application value.