The invention relates to a power grid infrastructure rainstorm risk assessment method which sequentially comprises the steps of data collection, risk assessment, and risk rating. The method has the following advantages: power grid infrastructure rainstorm risk assessment is conducted through data collection, risk assessment and risk rating; disaster condition data, rainstorm data, social economic data, basic geographic information data and grid distribution data can be used for reference; four elements causing rainstorm and flood risk to the power grid, including the degree of disaster-inducing factors, the sensitivity of disaster-breeding environment, the vulnerability of hazard-affected body and the ability to prevent and fight against disasters, can be calculated efficiently and accurately; and the rainstorm risk can be assessed comprehensively, and the power grid rainstorm water-logging disaster risk index is divided into different grades through risk rating, which facilitates observation by operators.