This paper expresses the study of runoff characteristics of typical rivers (Oyodo, Sendai, Kimotsuki) in Southern Kyushu. The non-linear analysis is used specially for the study of runoff. The basic equation can be expressed by Eq(3) for the runoff model. The linear and non-linear kernels are obtained by numerical calculation. The unknown terms are derived so that the squared sum of error between calculated discharge and observed one may be the least. From the results of analysis, it is found that even if it rains a little, the surface runoff occurs, and much groundwater runoff are expected at all times. The above is the runoff characteristic in Southern Kyushu. It is a reason that the surface soil always has much moisture content. Then, the annual total water losses show 600-800 mm except the Kimotsuki river. Those values nearly coincide with the national mean value. The evapotranspiration from river basin is not much affected by plant features, surface soil, geology and such conditions of it, but affected by water content in the subsurface stratum and the number of rain days.