This research covers up social activism of Jeju Buddhism during the period of Jeju 4.3 Incident. Jeju Buddhism launched the activist movements for pending issues of Jeju society after political liberation of Korea. Buddhists in Jeju were trying to restore their own tradition of Korean Buddhism and establish political autonomy of Jeju residents. However, Jeju Buddhism suffered from the severe oppression accompanied by their activist movements. Even now, the aftermath of 4.3 Incident still remains ineradicable to Jeju Buddhism. A lot of Buddhist monks were victimized with other Jeju residents without any judicial proceedings during anti-guerilla pacification operation. In addition, their properties including temples and Buddha statues were also devastated or plundered by the repression forces. For reconciliation of Jeju 4.3 Incident, we should pay attention to dedication of Buddhist activists and their sufferings under political violence during the 4.3 period.