One tools which is used in decision making for investing in a firm models of predicting bankruptcy. The aim of this research is to offer the best model of bankruptcy of firms in Iran. For this research, the logit model is used and a model is offered to predict bankruptcy in accepted firms in stock exchange of Tehran. For designing a model, the information of two groups of accepted firms are used in stock exchange of Tehran. The first group of evaluated firms was consisted of 20 bankrupt firms and the second group was also similar to first group and was consisted of 20 non-bankrupt firms. To design these model nine financial ratios were used. According to this research among these, the logit model with explanatory variables of working capital to total assets, current liabilities to current assets and gross interest to sales are liquidity ratios, liquidity and profit ability ratios respectively, which has the most powerful predictability about bankruptcy of firms in Iran. The accuracy and precision of predictability model for the year of bankruptcy is %87.5, for one year before bankruptcy is about %72.5 and for two years before that is % 52.5.Therefore the recent research has shown that the bankruptcy procedure of firms in Iran, not only is not a long term and gradual procedure but also these firms under the condition of economical fluctuations and political variables in short term were encountered with bankruptcy.