Exchange rate is one of the most important variables affecting macroeconomics. Therefore, foreign exchange regimes and policy rules used in exchange rate management are of great importance. One of the most important features of a currency system is its ability to achieve economic stability and control inflation, which is also mentioned in the strategy of the resistive economy. Accordingly, in the economy of Iran and some other similar developing economies, in order to reduce the adverse effects of various types of exogenous shocks, the managed floating exchange rate policy with a rule for periodic adjustment of the exchange rate has been selected. This study seeks to evaluate the principle of inflationary exchange rate determination rule (the rule proposed in the permanent decrees of Iran's economic development programs, as the case study) in reducing the inflation rate as well as reducing the instability caused by the implementation of erratic monetary and fiscal policies. In order to quantify the criterion of economic stability, two indices of “variance” and “autocorrelation” coefficient of the path of changes of selected macroeconomic variables in the transitional period after the occurrence of the shock are used. The research method of this study is the theoretical analysis and numerical solution of the simulated version of a DSGE model in the international economy (open small economy) that has been calibrated using the parameters of the Iranian economy. Based on the results of the study, the implementation of the inflationary rule of Exchange rate determination, in comparison with the discretionary approach of exchange rate management, will reduce the inflation rate and the growth rate of the exchange rate. Also, the implementation of this rule will reduce the instability of selected macroeconomic variables in response to the shock caused by the implementation of erratic fiscal policies as well as unconventional monetary policy, such as changes in the reserve requirements ratio, but will increase the volatility and instability caused by the implementation of erratic conventional monetary policy, such as changes in interest rates. Therefore, from the perspective of the resistive economy strategy, the inflationary rule of exchange rate determination, is preferable to the contingency approach, as it creates lower inflation rates and price growth rates, but in terms of managing and controlling the instabilities caused by the implementation of erratic monetary and fiscal policies, the choice of the preferred approach depends on the priority of the economic authority.