This paper proposes a multilevel security model based on trustworthy state

which introduces the concept of reliability and the function of integrity measurement.It enforces diverse security rules to different kinds of objects.To prevent running intrusions

the access ranges of subjects are adjusted according to their reliabilities.The formal description of the model and the transform of its trustworthy states are given in the paper.It is proved that the system remains in a secure state after performing the security rules of the new model.Moreover

its realizing framework in operating system kernel is described

and its performance is analyzed.