In 2009, after the end of the 26-year civil war, Sri Lanka's national security is still facing many challenges, especially the extremism dominated by the "Buddhist-Muslim" religious conflict is spreading. As the threat of Tamil separatism has removed, Buddhist extremist groups in Sri Lanka have begun to turn their attention to Muslims, exacerbating Buddhist-Islamic tensions. Buddhist extremists have further exacerbated tensions between Muslims and Buddhists by inciting hate speech and violence against Islam, fueling rising anti-Muslim sentiment. In 2019, after the Easter attacks by Islamic extremists, the Sri Lankan government took tougher measures to control the growth of extremism, but the results were not satisfactory, and religious extremism spread further. The relationship between Buddhism and Islam is mutually antagonistic and radicalized, showing a pattern of "reactive extremism". Buddhist nationalists see their religion and culture as threatened by “Islamization”, while Islamic extremism is gradually hidden under social marginalization and security pressures. Both extremisms are ideologically “defensive” and perceive their culture and religion as threatened by the other. Buddhism and Islamic extremism present a two-way interaction in terms of crisis narratives, acts of violence, and international influence, reflecting the interaction and intensification of these two extremist forces.