Abstract: Analyze the basic principles and implementation steps of ID3 and point out the advantages and disadvantages of two existing improved classification algorithms.With the shortcoming of inclining to choose attributes having many values for ID3 and the deficiencies of classification time and classification accuracy for existing two improved classification algorithms，a new attribute selection scheme is proposed and optimized with mathematical knowledge.Experiment results show that the optimized scheme can overcome the above disadvantage of ID3 and has the advantages of classification time and classification accuracy over the existing two classification algorithms.