Abstract: KNN (K-nearest neighbor) is the most famous pattern recognition statistical method,and it is widely used in text classification,image processing and other fields.Because of simplicity and realization based on case classification method,KNN can be used as entry case algorithm of artificial intelligence courses .For the lazy learning method in KNN classification process,it has some difficulty in the theory and practice teaching.According the study of KNN algorithm and the analysis and design of software teaching system,it has achieved the teaching system based on Visual C#,and includes practical teaching,improving the teaching methods and the quality of teaching.