The main focus of this study is on the area data generalization of Taiwan Bau-Tu. We compare the area discrepancy of the rice paddies and dry farmlands between Taiwan Bau-Tu and historical materials of I-Lan County. The results show that the differences are small, where the correlation coefficient reaches as high as 0.96 and the linear regression's coefficient of variation is over 0.92. If the area is analyzed after divided into groups, the land status of those under 5 Jia (almost equal to hectare) has more variation. For research topics on the land status of smaller areas, it is advised to take notice of the effects of generalization. Although generalization will tend to filter out some information, the discussion on the generalization of Taiwan Bau-Tu can let us understand the amount of errors and can do some contributions to correlative researches.