Today, one of the major problems of banks is the amount of their non-performing loans. The ratio of non-performing loans is used as a measure of bank health. Therefore, the purpose of this study is to investigate the factors affecting the ratio of non-performing loans. In this regard, the vector Auto Regressive– vector error correction model has been used to examine the effects of macroeconomic and financial variables such as business cycle, government debt, unemployment rate, foreign direct investment, and domestic credit by the banking sector. To achieve the research goal, quarterly data from 1996 to 2017 were collected from Iranian banks. According to the results of the study, the relationship between business cycle, government debt, and foreign direct investment and the ratio of non-performing loans is negative, while he relationship between domestic credit provided by the banking sector and non-performing loans ratio is positive. Unlike other variables, the unemployment rate variable has a short-term effect on the ratio of non-performing loans. According to the results of analysis of variance of the estimated model in the long run, approximately 48.96% of the changes in the ratio of non-performing loans, through the past values ​​of this variable, 41.42% by the government variable, 4.14% by the banking sector domestic credit variable, 3.12% by the unemployment rate variable. 1.3% is explained by the business cycle variable and 1.6% by the foreign direct investment variable.