The invention belongs to the field of power grid engineering cost analysis. The invention relates to a power grid project cost assessment method. The method comprises the following steps: sorting influence factor data in power grid engineering cost corresponding to a new technical situation primitive, and carrying out normalization processing; Construction of a sample database, screening key influence factors of the power grid project cost in a sample database based on a principal component analysis method, establishing an explanation structure model of the influence factors of the cost project, constructing a key influence factor system of the power grid project cost based on the explanation structure model, calculating influence weights of the key influence factors by adopting an analytic hierarchy process, and sequencing. According to the method, before principal component analysis is carried out on the power grid project cost data, normalization processing is carried out on the historical project data, initial data are preprocessed, and a guarantee is provided for the accuracy of follow-up data analysis.