If we open the history of Islam in the classical period, it will be found a fact that radicalism as a movement is not a new phenomenon in the modern Islamic world. Call it a religious sect in Islam as Khawarij is the most famous Kalam sect through radical understanding and uncompromising. This is evidenced by acts of violence to achieve its goals, as did the murder of the prophet’s companions post-agreement or tahkim (arbitration). Which is considered to have deviated from the God’s teachings.Therefore, in an effort to fill the lack of contemporary Islamic theology studies, in relation to radicalism, this research was conducted to analyze “how the relationship of genelogical between Khawarij understands in the classical period with contemporary radicalism movement of Islam today”. The analysis is done through a literature review, by examining a variety of written sources related radicalism. Also outlined some of the terminology associated with Islam radicalism. To be more focused analysis, this research could take a sample of Indonesia as a base of movement. It is important to look at the significant relationship of radicalism in the history of Islam. And then, the last part of analysis indicated a solution in an effort to prevent the development of radicalism movement escalation in Indonesia, in the form of radicalism therapy.