The purpose of this research is to distinguish the factors which influence the form of waterfalls. The defination of a waterfall in the study is of which the height is higher than 5m and will not dry around the year. The form discussed here includes five parts, the face of waterfall (the ratio of width and length), the inclination of fall wall, the existence of plunge pool, the appearance of cap rock, and the relationship between the dip of strata bed and river orientation. The study area includes four waterfall groups in the northern Taiwan, named Pinhsi, Tatun. Wulai and Chiaohsi group. The geological setting are quite different among four groups. There are 40 waterfalls investigated totally, 12 in Pinhsi group, 8 in Tatun group, 11 in Wulai group and 9 in Chiaohsi group, respectively. After classifying each kind of forms and factors of 40 waterfalls, I analyze the relationship between each kind of forms and factors with methods of contingency table and X2 test. The conclusions are as follows: 1. Waterfalls mostly are splender type according to the face form, inclined type to the wall form, horizontal type and reverse type to the bed form. However, there isn't a special type obviously on the form of plunge pool and of cap rock. 2. For waterfall belongs to the small scale landform, the form of it is controlled mainly by the factors of lithology.