Today, the discussion of regularity monetary policy in achieving inflation and output gap stabilization targets is important. In this paper, we investigated the persistence of output gap in Iranian economy. Using a hybrid New Keynesian model over the period 1990:1- 2011:3, we compared three alternative instrumental rules in monetary policy.The results indicated that in Iranian economy, first, output gap is forwardlooking and has little degree of persistence. Second, inflation targeting rule in comparison with the price level and speed limit targeting rule has the lowest social loss. In addition, the result of estimating coefficients under alternative rules showed that in comparison with other instrumental rules, inflation targeting and the first equation of price-level targeting have well predicting power, especially in long-term forecasting horizons.