Ensuring the reliable operation of the power grid is more challenging, and vital, than ever. Industry restructuring presents transmission system planners with a range of uncertainties that traditional methods cannot address. EPRI's Probabilistic Reliability Assessment (PRA) program offers energy companies new, more-accurate tools for assessing grid reliability under restructured market conditions. This paper presents the application of PRA program for Chongqing power, to obtain new insights into system behaviors and develop the benchmark of system reliability, which provides a way to integrate the planning and operation functions based on risk analysis. This work has demonstrated that the PRA method can better evaluate system risk level, assist information exchange between system operators and planners in order to maximize transmission system reliability and minimize the operational risk.