Abstract: Contemporary Humeans try to use the instrumental principle to explain the source of moral motivation, that is, if people desire φ and believe that φ can be achieved by moral action ψ, then they will have motivation to do ψ. The Kantians inherit Kant’s basic claim which opposed the claim that moral motive comes from people’s satisfaction of some natural desires, and believe that obedience to morality stems from obedience to the rules of practical rationality. But following Korsgaard, the obedience to the rules of practice also comes from the cognition of the value of practical life and moral behavior. Contemporary researches of neurophysiology have shown that Humean is more dominant in explaining the source of moral motivation. However, the Kantians have been constantly improving their own theories and combining Velleman’s autonomism with Korsgaard’s cognitive claims would be a feasible approach. The complexity of real life suggests that we’d better give up the multiple choice question between Humean and Kantian, because the former describes the source of the moral motivation of ordinary people, while the latter tells us how the ideal moral motivation of rational people should be generated.