Sentencing is the most important process in criminal law. On the other hand, the state can have more intervention and force to its citizens. Sentencing not only is the most controversial and sensitive area of criminal law but also is the vaguest area in criminal justice system. Sentencing is not as easy as it appears. Each crime, each criminal, each criminal trial is completely different from another one. Sentencing is an important concern for those who seek the judicial reforms. Recently, in the most countries around the world, the sentencing practices became reformed and sentencing based on gender, race, ethnic, socio-economic statues disappeared to some extent. There are four important schemes of sentencing: definite sentencing, indefinite sentencing, presumptive sentencing, and mandatory sentencing. This article tries to explore these schemes and explain the characteristics of each scheme. This article has comparative approach to UK criminal justice system and Iran criminal justice system.