Imprisonment is one the most common punishment in Iranian criminal policy, but it has numerous defects. It doesn’t realize training aims, so legislature and judicial authorities have to limit the use of this punishment as much as possible. The aim of this article is to review the effects of judicial factors including legislative and executive ones that cause increase in the size of criminal population in prisons and to present approaches to tackle this problem. Tendency to punishment and imprisonment in all members of society like individuals and families has made judges interested in imprisonment as the best way for crime prevention. This article analyzes the lack of ingrained measures for imprisonment and qualified judges to make use of them, the absence of criminological trainings and executive requirements of prison substitution and unwillingness of judicial authorities to accept the effectiveness of substitutes for imprisonment and etc. Iranian criminal policy faces fundamental difficulties in its judicial, legislative and executive aspects. In judicial sphere, the criteria of penalty definition have not been explained in an appropriate manner for judges. Providing criminological trainings for judges to change their attitude is the most necessary approach to prevent a surge in the prison population
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