Immense reserves of fossil fuels, has caused weak attention to economize energy consumption and has consequently led to energy waste. Also, due to data limitations, timeworn equipments and traditional structure of many industries, little research has not been done in the industrial sector from this point of view. This study uses of structural decomposition approach to survey changes in CO2 emissions in Iranian industrial sectors using tables of input-output in the years 1370, 1375 and 1380. The main factors causing the changes in the emissions are analyzed. Marginal demand has been most important factor of CO2 emissions augmentations in both periods (1370-1375 and 1375-1380). The structural changes in exports have improved, it has reduced industrial emissions. Technology improvement and industrialization, however, has had a mince impact on reducing emissions, but it has improved the level of exports as a factor in the reduction for the period is 1375-1380. During two periods, energy efficiency improvement has been the most important factors in reducing CO2 emissions in the “transportation”, “refining and production of petroleum products”, “production of other non-metallic mineral” and “production of basic metals”. It seems that for more reduction in CO2 emissions particular attention should be paid to this factor.