The changes in age and sex structure of population as an independent and primary factor- irrespective of other influencing factors- creates imbalance in marital situation of the society. Based on population changes in recent decades in Iran, especially in the period of 1976-1986, there has been a remarkable change in the age and sex structure of population. These structural changes of the population in Iran had different economic, social and cultural impacts in different time periods causing many types of economic and social hindrances in the society. As a consequence, presently we have to deal with over supply of labor and as the result a high rate of unemployment .Other expected impacts in the near future will be imbalance among girls and boys in the marital age groups. This imbalance will result in the increased number of single girls. The aim of this article is to study the issue in the three decades (1956-1986) and to discuss the relationship between changes of population age and sex structure and marital situation in Iran. Also, quantitative impacts of such changes on the future decade will be presented.