The present study was conducted on the effect of financial constraints and cash fluctuations on companies' business credit. The present research is applied in terms of purpose. On the other hand, considering that it investigates the relationship between two or more variables, it is descriptive and correlative in terms of nature and method, and considering that historical data has been used in doing so, it can be Classified by post-event type. The time frame of this research is a five-year period based on the financial statements of 1391 to 1397 of sample companies. However, due to the fact that to test the hypothesis in the first model, the variable of profit changes in year t compared to year t-1 has been used, in practice, the time domain of the research is a six-year period. Before analyzing the research data, the reliability of the variables is checked.The reliability of the research variables means that the mean and variance of the variables have been constant over time and the covariance of the variables has been constant between different years. As a result, the use of these variables in the model does not cause false regression order to determine the type of approach used, Limer, Hausmann, heterogeneity of variance, residual normality and serial autocorrelation tests are performed. The software used to analyze the data is Eviews. The results showed that financial constraints have a significant effect on companies 'business credit and also cash flow fluctuations have a significant effect on companies' business credit.