The aim of this research is to study and recognize a Part of risk process and its relation with the company's financial costs in Irons stock exchange. At first, it is a review of available theories in capital structure and the relationship between debt ratio and earnings per share. Then, the researcher gathered the financial data of the public corporation, so, he choosed an 86 member sample through 12 industries and tested two complementary hypotheses. In the first studied hypothesis — which it is used of the linear regression model and the whole industries for it the results showed any linear meaningful and positive relation between financial lever and the systematic risk. In the second hypothesis test, the typical companies classified on the basis of trade risk index with using of LSD test. Then, in every risky class, the validity test of different financial lever was accomplished (with the use of ANOVA test).
Finally, with deviation comparison test, the relationship between financial lever and the systematic risk of companies was studied. Also, the result of this test leads to lack of meaning full dispersion in the company's systematic risk, after debt increasing. (In comparison with before debt increasing).