Criminal law of our country in the last three decades has been inflated hard. Criminal Code, regardless of the data and results Wathiq criminology, is unusually thick. So this thesis to evaluate the need to reduce criminal categories in Iranian law was designed. A qualitative study of descriptive-analytic study. The data collection tool library. Information analysis was performed for descriptive and analytical. The results showed that the legislature can enact laws provide clear and explicit efforts to reduce criminal categories. The results showed that the constitution only in terms of appropriate action to prevent crime is event is planned without appropriate mechanisms and tools and the scope of powers and duties of the judiciary in this regard has not been set Therefore, the circle and the extent of "appropriate action" should also explain to prevention within the scope of the rules to be implemented. Of course, in prevention and decriminalization of laws, attempt to explain the purpose of the judiciary but also requires collaboration with other forces. Generally, the results showed that inflation causes multiple criminalization of criminal law in the present system can be; the Islamic legal system, various legislative bodies, the huge wave of technology, lack of attention to the collective conscience and to criminalize for use trick in the criminal law and other factors named.