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The ability of OLG models in analyzing and simulating the various fields of an economy, such as the investigation of endogenous growth policies, the development of intergenerational equity criteria and the reform of social security system, has caused these models to have a special position among economists in recent decades. However, difficulties in quantifying these models and analyzing their stability properties have led them to remain only theoretical and receiving less attention from empirical viewpoints. This paper uses the proposed method by Auerbach and Kotlikoff to estimate a 55-period overlapping generations model. Then due to failures of the Iran’s Pension System, it analyses and simulates Pension System within overlapping generation’s model with heterogeneous agents living in 55 periods. Thus we study the effects of transition from the Pay-As-You-Go Pension to the Fully Funded Pension System in the process of capital accumulation, national production and national consumption. The findings indicate that the individual optimal consumption-saving behavior varies under different social security systems. The results of the simulation model show that in addition to increasing the personal financial assets, Fully Funded Pension System provides a higher physical capital accumulation for the economy than that of ‌Pay-as-you-go Pension System. In addition to higher levels of national consumption and production, the transition to the new system causes people to have more incentive to stay in the labor market and to complete their career because they have higher labor income than the old pension system.