In this paper, we define a differential module and study its properties. In section 2, as for propositions, we research some properties, directsum, isomorphism of factorization, exact sequence of derived modules. And then as for theorem, I try to present the following statement, if the sequence of homomorphisms of differential modules is exact. Then the sequence of homomorphisms of Z(X) is exact, also the sequence of homomorphisms of Z`(X) is exact. According to the theorem, as for Lemma, we consider commutative diagram between exact sequence of Z(X) and exact sequence of Z`(X). As an immediate consequence of this theorem, we obtain the following result. If M is an arbitrary module and the sequence of homomorphisms of the modules Z(X) is exact, then the sequence of their tensor products with the trivial endomorphism is semi-exact.