Power grid projects are related to national economy and people's livelihood. It is particularly important to control the cost. And when controlling the cost, it is a key link to evaluate the cost. In the actual cost evaluation of the past, it is commonly used to compare the settlement amount with the approved budget amount. However, this method is more general. And it has strong subjectivity. In this paper, the probability analysis and the power grid project evaluation are combined. Based on the past similar projects cost library, realize the standardization, rationalization and objective of the cost evaluation. Finally, take a substation and a line project for actual evaluation. The results show that this technology can realize the intelligent evaluation of power grid projects, which can be further promoted and applied.