Abstract: Folk psychology, a widely influential theory in contemporary philosophy of psychology, focuses on causal explanations and mindreading for mental activities. However, it has been questioned by many philosophers, psychologists and cognitive scientists that causal explanations were based on platitudes and mindreading was accounted for a functionalist strategy as a working way in folk psychology. The puzzle for folk psychology is, not its use of the methods from scientific psychology to explain mental states but, its underlying theory which is followed when it explains causations of everyday behaviors and mental states. An analysis of folk psychology from the philosophy of psychology, displaying the puzzle in folk psychology, will help us better understand its statue in contemporary psychology. Due to the evidential difference between the explanative levels in the folk and scientific psychologies, the best way to solve the puzzle of folk psychology is to construct the interface of explanations between the person level and the sub-person level.