Mind wandering is an important part of the stream of consciousness, which allows the stream of consciousness to continue when the individual does not process external stimuli or does tasks. The neural mechanism of mind wandering is the current research hotspot. This study involves the brain’s default network and two theories of different positions, one is the theory of executive control, and the other is the theory of executive control failure. The study discusses adaptive functioning of mind wandering, especially in terms of creative problem solving. Finally, there is a discussion of how to reduce the negative effects of mind wandering—mindfulness training.