ABSTRACT Political parties institutionalization is not a top priority in efforts to institutionalize democracy in Indonesia. The study of the political parties institutionalization is often measured with strong and weak of the institutionalization itself rather than on how the institutionalization process took place. For this purpose, this study tries to trace how the transformation process of political parties institutionalization in Indonesia happened. This study takes a case of PKB institutionalization transformation in Gus Dur Era (1998-2008) to Muhaimin Iskandar Era (2009-2014). To explain the transformation process of institutionalization, this study uses Randal and Svasands (2002) concept of institutionalization who tend to see the party institutionalization as a party management scheme based on four dimensions, namely the dimensions systemness, infusion values, decision autonomy, and reification. In order to elaborate the way of transformation institutionalization in PKB in the year of 1998-2014, this research uses case study method which is a type of qualitative research. This study is limited by space and time, the party organization and the periodicity of time between 1998 to 2014. To make the operationalization of the data simple, this study is divided into two periods, the Gus Dur leadership period (1998-2008) and the Muhaimin Iskandar leadership periods (2009-2014). Then, both periods are analyzed by four variables of party, namely systemness, the value of infusion, decision autonomy, and reification. The two periods then produce a study conclusions regarding changes in the pattern of institutionalization of Gus Dur era to Muhaimin Iskandar era. The changing pattern is then referred as the transformation of the political parties institutionalization. The results of this study indicate that PKB had been transformed from Gus Dur Era (1998-2008) to Muhaimin Iskandar Era (2009-2014). Firstly, in the dimensions of systemness, PKB institutionalization pattern began to change from the pattern of intra-party power management which tends to converge to one of specific oligarchic figures to the management of intra-party democratic which tends to spread the posts of power to many figures. Secondly, the infusion valur dimensions, PKB institutionalization patterns began to change from unsolid party that always raises factionalization intra party to a solid party, so there was no factionalization anymore. Thirdly, in dimensions of decision autonomy, the institutionalization of PKB pattern began to change from independent which never join the system of government cartelization to the institutionalization patterns that tend dependent with institutions outside the party which always be included in the system of government cartelization. Fourth, in the dimensions of reification, PKB institutionalization pattern began to change from the pattern of building the public imagination as NU party and tend to use a sociological approach to religion in electoral strategies to establish a pattern of public imagination as a modern party that open and begin to accommodate a rational approach in electoral strategy. (Keywords: Political Parties, party institutionalization, Transformation Institutionalization, Systemness, Value Infusion, Decision Autonomy, Reification)