Similarity appraisal accounts for a great part of appraisal area. Therefore, we need effective method for similarity appraisal. The judge, Learned Hand, suggested a theory called abstraction - filtration - comparison, we apply the theory to similarity appraisal. The abstraction step are analysis methods and criteria for analyzing source program. The filtration step to exclude contents and items in source programs. The comparison step analyze filtered source programs using analysis tool.