Internal Audit has a critical role in managing and conducting the organization's operations. Organizations with an efficient and effective Internal Audit department, can more accurately evaluate the risks of businesses, processes and commercial systems. In current research, by using Delphi research methodology and a survey of 210 professional and academic experts, it was tried to identify the Internal Audit quality criteria approved by the experts, in order to design a suitable model for the Iranian environment. For this puepose, based on the literature review and the research background, 29 criteria were identified which were classified in four sections including: a. Competence of Internal Auditors with eleven criteria; b. Independence of the Internal Audit department with eight criteria; c. Criteria related to the performance of Internal Audit work with seven criteria; and d. Other criteria with three criteria. Data were analyzed by utilizing “ R” software with a confirmatory factor analysis model. The results of the study indicate that 18 criteria have been adopted, which provides a model for the quality of Internal Audit.