This paper adopted the classical recession curve based on GA to study and analyze the mean daily runoff at some hydrological stations in the Xijiang upstream. The accuracy of verified results demonstrate well with Nash coefficients. Therefore, the obtained coefficient of recession can reflect the characteristics of the study basin. This paper also studied the relation of the coefficients of recession with the catchment area, underlaying surface characteristics, degree of vegetation and mean annual runoff, and discovered that （1）The recession coefficients will decrease with the catchment area and vegetation degree increasing; （2）The recession coefficients will decrease with the height difference permeability of underlaying reducing;（3）The recession coefficients are especially sensitive to the Karst landform, characterized by being larger than those in the non-Karst area;（4）The recession coefficients will increase with the mean annual runoff increasing, and there is an exponential function relationship between the two. These rules between the recession coefficients and catchment characteristic factors will provide reference for runoff forecasting in ungauged basins.