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In This paper energy intensity has been decomposed by ideal Fisher index into structural and intensity effect. Results show Structural effect doesn't have considerable changes and the amplitude of fluctuations is around 0.95 and 1.06. Structural effect is slightly more than 1, it means economic activities tend to produce commodities which use more energy but the small change in the share of economic activities has trifle effect on higher energy intensity. However Intensity effect which shows changes in energy intensity independent of compound of economic activities has raising trend. Expect in 1982 intense effect is more than one and means more energy has been used for same commodity. Rising trend of intensity effect shows that waste of energy and inefficiency have risen. Trend of aggregate energy intensity, ratio of energy intensity of current year to constant year, is like intensity effect and influence of structural effect on it, is negligible.