Abstract: In a famous scholar of American named A John Simmons' article "Justification an d Legitimacy", he discussed two dimensions of institutional evaluation—the jus tification of the state and state legitimacy. Aiming at the familiar mixture or improper definition of them in contemporary political philosophy, Simmons adopte d Lockean approach and Kantian approach to show the relations between justificat ion and legitimacy. And differentiating the two concepts has a very important si gnificance in the research of the normative theories of the state.