The aim of this paper is to elaborate the strength of interest group coalition in influencing public decision making by a coalition strategy. In terms of stakeholders’ analysis in public policy formulation, there are many influential actors divided into two groups which are the official policy makers (executive, legislative, administration and judicial branches) and non-governmental participants (political parties, interest groups, think tanks, mass media and citizens). However, regarding to some views of scholars, political parties are more able to influence than interest groups in decision making process. Parties are formal institutions that could place their members as lawmakers in a legislative branch. Nevertheless, in terms of this research, it could be concluded that interest groups are willing to be more powerful if they have own strategies by developing a coalition among other civil societies. There are two critical aspects that must be discussed in this research. The first is to describe the stages of coalition development and the core values of coalition engagement. The second is to elaborate the strength capacity of coalition in running some various ways both conventional and non-conventional to influence the final decision making. The research was conducted by a qualitative method while the data are collected by interview and analyzing various documents.