Abstract: On the basis of the BLP model and RBAC model，a new improved multiple-level model is presented.The improved model has four important features：（1）carry out the control of integrity；（2）constrain the trusted subject and limit the right of other subjects；（3）realize RBAC model to assign the role and the permission；（4）fulfill the audit mechanism rules to monitor the security policy.Experimental results show that the improved model increases security and the usability.

Key words: control of integrity, trusted subject, Role-Based Access Control（RBAC） model, audit mechanism

摘要： 在分析BLP模型和RBAC模型及其相关衍生模型的基础上，提出一种改进的模型。改进模型主要有4个重要特点：（1）实施完整性控制，保证信息流上写安全性；（2）限定可信主体，赋予其余主体有限特权；（3）实施RBAC模型，分配角色和权限；（4）引入审计机制，提供策略监控。实验结果表明，改进后的模型在完善安全性的同时提高了实用性。

关键词: 完整性控制, 可信主体, 基于角色的访问控制（RBAC）模型, 审计机制