Abstract: Mind wandering, or daydreaming, is referred to the phenomenon that the conscious experience of human being was spontaneously occupied by the internal mental representation, and it is such a ubiquitous status that everyone could experience everyday. Although mind wandering was regarded as the BUG in the attention system of human being, with the deeper and deeper understanding of mind wandering, the researchers have began to take a more comprehensive view of mind wandering, including its costs and benefits. Today the hot interest of the human brain energizes the study of mind wandering. Mind wandering is not only the working style of human mind, but also the embodiment of the intrinsic self-organization in the human brain. We describe the phenomenon of mind wandering, its research progress, and the principle view in this field. The prospect of the development in the research of mind wandering is given in the end.