The invention belongs to the power transmission line risk early warning assessment technical field and relates to a Poisson distribution-based power transmission line tripping risk assessment method. According to the method, a regional power grid is divided into a plurality of meteorological regions according to historical meteorological data; ledger information, meteorological information, tripping information and the like of a power transmission line are organized according to the regions; a power transmission line fault rate distribution formula is established based on a Poisson distribution equation; meteorological parameters in the meteorological regions are segmented; distribution parameters and meteorological data of meteorological blocks are put into statistics; and a regression analysis method is adopted to establish a power transmission line tripping probability distribution model of wind and rain weather parameters, wherein the power transmission line tripping probability distribution model is used for assessing tripping risks under heavy rain and strong wind environments. According to the Poisson distribution-based power transmission line tripping risk assessment method of the invention, the tripping rate of the power transmission line is analyzed, and with the increase of statistical data, the accuracy of the method is continuously increased; and Poisson distribution is adopted to perform risk prediction, and therefore, the method is more suitable for random event prediction of an approaching time period.