Abstract: With the continuous increase of power grid investment in recent years, the necessity of controlling project cost investment is becoming more and more prominent. With the application of new technologies and new schemes, the traditional cost index of transmission line project can not accurately reflect the level of project cost. In order to solve this problem, we apply the GM (1, 1) model of grey correlation theory, and collect different years of transmission line project data. We make a prediction that the main material price to influence the project cost accounts for the proportion of the whole project investment as the research object. We make the rational adjustment, according to the results of prediction for the future material price controls, in order to achieve the purpose of project balance ratio decreased.