Knowledge acquisition is the bottleneck of expert system. To solve this problem, KD (D&K), which is a comprehensive knowledge discovery process model cooperating both database and knowledge base, and related technology are proposed. Then based on KD (D&K) and related technology, the new construction of Expert System based on Knowledge Discovery (ESKD) is proposed. As the key knowledge acquisition component of ESKD, KD (D&K) is composed of KDD* and KDK*. KDD*-the new process model based on double bases cooperating mechanism; KDK*- the new process model based on double-basis fusion mechanism are introduced, respectively. The overall framework of ESKD is proposed. Some sub-systems and dynamic knowledge base system are discussed. Finally, the effectiveness and advantages of ESKD are tested in a real-world agriculture database. We hope that ESKD may be useful for the new generation of expert systems.