The invention relates to the field of power transmission and transformation projects, and particularly relates to a power transmission and transformation project cost prediction method. The power transmission and transformation project cost prediction method comprises the steps of collecting cost data of built power transmission and transformation projects; carrying out classification and preprocessing on the cost data; carrying out discrete time division on the processed substation data so as to form a data set; carrying out cost data mining, and realizing mining for data member association rules in a historical database; carrying out mining on pre-built project related data, and realizing mining for the pre-built project data and the data member association rules in the historical database; and providing a service interface, and realizing external output of the data member association rules. According to the invention, the cost level of a project to be built is evaluated by using data mining technologies and a situational prediction method, and scientific and effective comparative prediction studies are carried out by being combined with cost analysis data of similar completed projects and comprehensively considering variations of major situational factors.