Abstract: In the construction of a building project, there is a very important link, that is, the audit of the construction project cost. It can reduce the cost of the project under the premise of ensuring the quality of the project, so as to expand the economic benefits of the enterprise. To ensure that the audit of the project cost is in line with the actual cost, it is necessary to do a good job in cost control of the entire project, and this kind of control work must run through the entire process of the project. At present, the most important task of cost audit work in construction projects in our country is to strengthen the cost control of the whole process of the project. Therefore, it is very meaningful to discuss how to strengthen the application effect of cost control in cost audit. This article will briefly describe the concept of cost control, then analyze the current problems in the use of cost control in our country, and propose effective solutions, and finally explain how to reasonably use cost control in cost audits with actual cases.