The transformation of Islamic religious education among adherents of Lom ancestors' beliefs is one of the essential factors of Lom believes conversion. Islamic religious education has been performed for a long time informal school process and in non formal process. The study was conducted in-depth regarding the Conversion of the Lom belief through the transformation of Islamic religious education scattered in several villages and sub-districts in Bangka Belitung province. This study was an ethnography study with a religious-anthropological approach and used the functionalism theory of Parsons. Data collection used observation, in-depth interviews, and documentation. The results showed that generally, the conversion of beliefs was occurred through the transformation of Islamic education in schools and community activity, besides the marriage factor. Even though they have become a Muslim, but they still endured and performed the cultural system of ancestor belief.