Abstract: By introduction of a new concept on the concern degree of information, the paper presents a novel matrix information security function, based on the confidentiality, integrality and availability, and at the same time a read-write axiom is defined. For arbitrary circumstances, the new security function corresponds to that in BLP model and Biba model. The security function value is used to make the safety classification of an object and the information flow policy is specified by the function value of two objects. As a result, an application information flow model is obtained. By a strict proof in mathematics, this model proves to be viable and safe. It is an expansion of the information flow model based on BLP model and the information flow model based on Biba model.