The main reason which brings about the separation between material outlook and practice viewpoint,truth view and value standpoint,practical materialism and dialectical materialism,dialectical materialism and historical materialism,comes from the separation between theory of practice and of dialectics in our present textbooks of Marxist philosophy. Thus,the unification between theory of practice and of dialectics is the precondition to realize the unification of the other categories. The essential reason causing above separation is due to the lack of internal relation between the concept of practice and of contradiction understood by Chinese Marxists. In order to make them unification again,the fundamental way is to follow the principles of unification between thinking and being,knowing and doing,which regards the relation between subject and predicate in proposition as the relation of subject and object in real world. Marxist theories,such as objectification,self-alienation and alienation sublation,have provided us with a model of practical dialectics of opposition and unification between subject and object.