Folk music can express the real aspect of social life. In addition, there are close relations between folk music and custom. Acutally folk music was formed, developed and variated in the folklore activities. The society of Taiwan is one kind of immigrant society. That is, its habitants are from different sources, such as the natives, Fukien Fu-lao and Hakkas,…etc. Therefore, folk music of Taiwan is rich in various contents. According to different people groups, the musical systems of Taiwan folk music are grouped into the native music and Taiwanized Han music. The native music persists considerable ancient southern island culture. As to Han music, it developd from Chinese traditional music. Some of Han music remain original appearance of Chinese music. Taiwan Han folk music is made up of folk songs, folk sing and dance, music of popular narratives, music in Chinese opera and folk instrumental music. This essay is titled "To Investigate Folk Music in Taiwan" because the author tries to investigate all the above points.