Oil-exporting countries often escalate macroeconomic fluctuations by adopting cyclical fiscal policies. Empirical evidence shows that the main reason of instability in oil-exporting countries is the poor management of oil. In this study, after introducing a small open macroeconomic model with a dual managed floating exchange rate regime and estimating it using quarterly macroeconomic data of Iran, five fiscal rules, balanced budget rule (BBR), counter cyclical rule (CCR), structural surplus rule (SSR), government expenditure rule (EXR) and government revenue rule (INR) were introduced. To select the appropriate fiscal rule for Iran, two approaches are used: loss function and Bayes ratio approaches. The results show that both statistical and welfare criteria confirm that the appropriate rule for the Iranian economy is the SSR financial rule. In other words, because the bulk of government revenue comes from oil sales, following a structural budget surplus rule minimizes the negative effects of sharp fluctuations in oil, and the government budget is much better balanced. Also, a single-float managed exchange rate system, along with the selected fiscal rule, leads to higher social welfare.