Regarding the limitation of conventional solution pertinent to the risk assessment and the actual requirements of power grid, a risk assessment strategy based on failure chain search is proposed. For the modeling of failure chain search, some improvements including the consideration of multiple fault types, the introduction of transient stability, voltage stability, frequency stability and system splitting criteria with the match of emerging prevention and control measures are proposed. For modeling of risk assessment, a fault correlation factor combined with the historical data of power grid is proposed to enhance the feasibility of failure chain probability. Moreover, the corresponding risk indices based on the Decree No. 599 of the State Council are designed. The risk assessment system is designed and developed finally. Simulation results are performed on a real-sized power grid in China to verify the validity and reliability of the proposed method, and some meaningful conclusions are drawn. This work is supported by National Key Basic Research Development Program (No. 2013CB228203).