Currently, the increase in the number of prison population is a major issue for the worldwide judicial system and Iran is one of them. According to formal statistics, the rate of prison population in Iran (per 100000) is up to 283 in 2014. However this proportion of overpopulated persons in Iran is very unfavorable in comparison with the rates of inmates in some other Asian courtiers such as Nepal (26) and India (30) per 100000 . The penal inflation which is resulted from unreasonable criminalization will have disastrous effects. While, the punishment shall be last resort for the combat against crimes. It will be used as the first solution in the criminal policy of Iran.Implementation of the new Islamic Penal Code (2013) can reduce criminal over population.