The relationship between exchange rate changes and trade balance has always been one of the major issues in theoretical literature and policy circles. A new approach to theoretical literature and empirical work suggest that the interaction of these two variables depends on a number of issues, including how each country's export and import markets interact, and the degree to which exports of goods are dependent on imports. For this purpose, in the paper, the relationship between exchange rate and trade balance in the Iranian economy is examined by considering the crucial role of Intra –industry trade in the form of smooth transition regression model for the period 2001: 4 to 2018: 4. The results showed that the coefficient of effect of the exchange rate on the trade balance in each period is affected by the intra--industry index, so that the lower the index, the less the effect of the exchange rate increase on the trade balance, and as this index improves, the impact is greater. This means that the positive effects of money devaluation on the trade balance can be benefited when the competitiveness of domestic products with similar foreign goods in each sector increases.