Economic participation rate is one of the key indicators of labor force in whole world such the amount of the rate could be determine the international economic level of country and it is utilized for codifying employment policy and planning. We have studied in this paper the reasons of the low level of economic participation rate in Iran during 2004-2009.We have shown economic participation rate has a downtrend except in 2009. Comparison of this rate in Iran and other countries shows not very suitable situation. Finally, this rate is evaluated in terms of the age, sex, … groups and the reasons of downtrend.