Key management is critical technic of realizing database encryption . in this dissertation, after analysing and comparing several popular key managemet scheme . we make improvement of two-phase key management scheme according to the matter of fact, and achieve two-phase key management scheme from user key to user class key and to data class key, through creating system table in database . at the same time, we work out key using sequence of chaotic nonlinear system . chaotic sequence is complex and recalcitrant to analysis and unpredictableness, and it can offer good complexity and comparable randomness . experiment result proves that using chaotic sequence can create good key 本文首先分析比较了几种常用的密钥管理方案,然后针对应用的实际情况,对两级密钥管理方案进行了改进,通过在数据库中建立系统表实现了由用户密钥得到用户类密钥、以及由用户类密钥得到数据类密钥的两级密钥管理。同时,本文利用由混沌非线性系统迭代产生的序列来生成密钥。混沌序列结构复杂,难以分析和预测,能提供很好的复杂性、类随机性。