Marx constructed his theoretical framework by using "criticism" rather than "moral preaching", whilst moral criticism and political economy criticism constitute the dual dimensions of his labor ethics. On the one hand, Marx employed religious and legal philosophical criticisms to complete the reversal of the moral and practical levels. On the other hand, starting from religious and moral criticism, and extending to political economy, Marx achieved a scientifi c criticism on capitalism. Moral criticism, as the starting point and intrinsic connotation of political criticism, refl ects the basic standpoint of historical materialism throughout, so is the ethical direction under political economy criticism. The goals pointed to by both theories are to achieve human freedom and liberation and are of a high degree of internal consistency. Through the transformation of the dimension of criticism, Marx pushed his thoughts on labor ethics to a deeper, more comprehensive and ampler stage of argumentation.