Abstract: By using the methods and technology of knowledge engineering, with the help of the technology of uncertainty reasoning, multi media, friendly human computer interface, and cooperative conflicts resolution, and having considered many kinds of factors that may cause corn insect pests and uncertainty in these factors, a farmer oriented, corn insect pests prevention and control expert system is realized. As a part of National 863 Advanced Technology Projects “Suihua Multi media Maize Production Expert System” and “Maize Production Intellectual Information Technology Application and Demonstration Project in Jilin Province Central Region”, this system has achieved good results in its application in the demonstration districts of Suihua City, Heilongjiang Province and Yushu City and Nongan County, Jilin Province.