The invention relates to a power transmission line icing state assessment method based on information fusion of multiple sensors. The method comprises the following steps: (1), obtaining an environment temperature and environment relative humidity, determining whether an icing condition is reached, and if so, executing step (2); (2), obtaining an environment temperature difference, icing duration and an icing thickness, and according to expert experience, calculating icing membership values of the environment temperature difference, an equivalent icing thickness and the icing duration; (3),performing data fusion on each icing membership value by use of a BP nerve network, and respectively calculating an icing-free probability, an icing probability and a severe icing probability; and (4), according to the icing probability, the severe icing probability and the icing duration, outputting an assessment result. Compared to the prior art, the method provided by the invention has the advantages of accurate assessment and the like.