In this paper, the author summarized and proposed five important issues in the present field of knowledge discovery and data mining, which comprise two important core issues, two conjectures, challenge issues in mainstream development, important issues of relevant fields in appliance research and technique standard in knowledge discovery (data mining).Some achievements and special analysis was also presented. Those five issues correlate closely, and these researches will push the development of knowledge discovery (data mining) to a higher stage, and bring great influence to the field inside and outside.