This paper deals with the Al-substitution of goethite in paddy soils and their original soils. The change of Al-substitution of goethire during the develoment of paddy soils was stutdied and its significance in soil classification is discttssnd. Cinder the artificial waterlogged condition, the Al-substitution of goethite in soils was weakened. the Al-substitution of goethite in paddy soils was much less than that of their original sails, and it decreased with soil developing. The change of Al-substitution of goethite in the diagnostic horizons not only reflected the special pedogenic condition of paddy soil, but also the characterized pedogenic process, So, it can be used as one of the major indices for dividing the subgroup of paddy soil. The Al-substitution of goethite was 9-18 mol% in the percogenic horizon of percogenic paddy soil,.but it was lower than 9 mol% in the periodically,waterlogged horizon of periiodically watterloged paddy soil.