Increasing the number of audit firms and increasing the level of expectations and environmental changes make the issue of competition among audit firms more complex and reveal the levels of information for users and stakeholders more dynamic. The role of audit firms is considered to be critical to the promotion of social trust, and institutions that do not have the ability to compete in this field are condemned to failure. This study sought to understand the role of design and functionality audit institutions in promoting social trust. The Research period is one year from 2016 to 2017. The methodology of research is mixed and the Statistical population consists of two qualitative and quantitative sections. In the qualitative section, 14 faculty members and associate accountants as panel members were selected through a homogeneous sampling method, of which 10 were contributing to the Critical Appraisal papers. In this section, papers similar to the topic of research on the inside and outside were determined based on the score of 50 points, and then the indexes related to the topic were developed in the form of checklists and distributed among 14 members of the panel (experts), based on Delphi indexes Such as average, standard deviation and agreement coefficient, the research indicators are confirmed. In the quantitative section, the target community was composed of 12 auditing firms, with 96 auditors selected through random sampling and Cochran formula selected by auditors working in 12 auditing institutions, and distributed after Delphi verification questionnaires. In this research, two main questions were raised in the qualitative section and two hypotheses were presented in the quantitative section.
 The results were in line with the research questions identified, the capabilities of the audit firms were divided into two internal and external components, each containing 4 indicators. Also, social trust was classified into three components of ethical accountability, legal accountability, and decision making power enhancement based on Delphi analysis and average score scores, standard deviations and agreement coefficients. In order to test the hypothesis of the research in the quantitative part, analysis of variance was used based on average severity test And the results showed that when the dimensions of the internal and external capabilities of the audit firm are matched, the internal capabilities indicators are consistent, and the external capabilities indicators are consistent, while confirming that the audit firm has the capability And empowerment, promotes the level of social trust of stakeholders and decision makers. The results are conceptually consistent with the research by El Ghoul et al (2016) and Ba (2016).