The invention relates to a method and device for generating a cost index of a power transmission and transformation project. The device comprises a model acquisition module, a sub-node index acquisition module, an index weight acquisition module, a father node index calculation module and a father node index output module, wherein the model acquisition module is used for acquiring a preset index model; the sub-node index acquisition module is used for acquiring a sub-node index according to the preset index model; the index weight acquisition module is used for acquiring the index weight; the father node index calculation module is used for calculating a father node index of a father node corresponding to the acquired sub-node index according to the preset index model, the index weight and the sub-node index; and the father node index output module is used for outputting the father node index. According to the method and device disclosed by the invention, the preset index model is acquired, and the sub-node index and the father node index are calculated according to the preset index model so as to ensure that the finally-acquired index can be more accurate, the error rate can be lower, and the generation efficiency of the father node index can also be higher.