Abstract: Abstract:This paper describes a program called KUP which analyzes and unders- tands PROLOG written by novice programmers.KUP takes as input a subject of the user's requirements,and gives many forms of equal-value programs with a series of operation on knowledge base.On the other hand,KUP also takes the user's program.as input.By analysing and understanding the program,KUP can decide the program corre- ctness in certain range and gives information for buggy program.