Economy refers to the total cost consumed in the process of planning, investigation, design, construction and use of the construction project, which is closely related to the cost of design, construction and use. Therefore, through the comparison and analysis of all the costs, scientific and reasonable evaluation can be conducted by means of technical and economic means, so as to judge whether the project is within the range of economic requirements, and make the overall value of the construction project significantly improve within a certain range as far as possible.