The research aimed to analyze and test the relationship between the audit firm reputation and the degree of its industrial specialization, and the extent to which there is an effect of the audit client's industry characteristics as Moderator variables for this relationship, which are the degree of concentration, the level of homogeneity, the degree of accounting complexity.Based on a sample of companies listed on the Egyptian Stock Exchange for the year 2020, 145 observations were extracted, each observation represents; the proxy of audit firm reputation, the level of its industrial specialization, and the measures of the characteristics of Audit Client's Industry. The research concluded that there is a significant effect of the audit firm reputation on the degree of its industrial specialization.The research also concluded that the degree of accounting complexity only leads to a fundamental difference in the impact of the reputation of the accounting and auditing firm in Egypt on the degree of its industrial specialization. While it was not found that there was no effect of the difference in the degree of concentration of the audit client industry, or the level of homogeneity in the audit client industry.