High-quality internal auditing brings various benefits, such as improving internal controls, deterring management misconduct, increasing the timeliness and quality of financial reporting, and limiting earnings management. The purpose of this research is to examine the relationship between the overlap and expertise of the head of the audit committee and internal audit implementation methods. This research is applied in terms of purpose and correlational in terms of nature and causal method. The statistical population of the research was all the companies admitted to the stock exchange in the period of 5 years from 1395 to 1399, and a total of 102 companies were studied through systematic elimination sampling. The dependent variable of the research is internal audit implementation methods and its independent variable is the overlap and expertise of the head of the audit committee. Generalized regression model and combined data were used to test the research hypotheses. The findings of the research showed that there is a positive and significant relationship between the financial and accounting expertise of the head of the audit committee and the internal audit implementation methods. But there is no significant relationship between the overlap of the head of the audit committee and the internal audit implementation methods. Therefore, despite the expertise of the head of the audit committee, internal audit implementation methods will be strengthened.