The invention provides a subarea assessment and early warning method and system of geological disasters of power transmission lines. The method comprises the following steps: obtaining a plurality ofindex subarea distribution maps based on assessment index data of risk assessment areas of the geological disasters of the power transmission lines and pre-divided a plurality of subareas; performingcalculation on the index subarea distribution maps on a geographical information system by using a risk assessment model to obtain a risk distribution map of the geological disasters of the power transmission lines; and performing power transmission line area risk assessment and power transmission line tower risk assessment in the risk distribution map of the geological disasters of the power transmission lines based on the assessed area. According to the subarea assessment and early warning method provided by the invention, the assessed area is divided into a plurality of subareas, respectiverisk assessment systems are respectively determined according to the geological environment features of the subareas, differentiated subarea assessment is carried out, and especially for the risk assessment of large-area geological disasters, the assessment results can be more accurate.