Investment estimation is one of the important links in the preliminary work of capital construction. It is a decision-making document and an important basis for studying and analyzing the economic effect of construction projects. After the reliability study report is approved, the estimate will be used as the investment limit issued by the design task, control the preliminary design estimate, and serve as the basis for fund-raising and bank loans. Therefore, in the economic work, we should realistically reflect the design content, reflect the economic situation of the construction area, and correctly and completely reflect the construction of the project from the beginning of estimation.