ABSTRACT The prediction of tourism demand has been an important factor as tourism planning is proceeded. According to some references, the number of prediction methods is more than 300, and these methods used in the estimation of tourism demand are involved with ARIMA, Regression Analysis, Gravity Mode. However, these methods can not afford to deal with the swift transformation of the inner and outer factors, because they need a lot of data. The appearance of Grey System Theory may provide a new direction to solve these problems,and it can build a model to predict the tendency of tourism demand through Grey Generating and error examination under the unreliable environment. This research try to arrange Taiwanese National Scenic Area in different divisionsn and predict the number of the tourists in National Scenic Area. The result shows that this theory can provide more accurate prediction in any divisions. Furthermore, it also proves that the accuracy can be improved through the predictions of more detailed units rather than an abstract division. As a result, this paper implies the restriction of grey predicting theory and provides more accurate way in predicting the number of tourists with the method.