The study area of this paper was located in the Pingjiang watershed, the typical soil erosion area of Southern China. Qualitative and quantitative benefits comparative analyses of soil and water comprehensive management were made based on the long series of historical observational data and runoff distribution theory. The results shown the ratio of runoff between flood and dry season decreased significantly from 3.51 (years from 1958-1979) to 2.45 (years from 1980-2015), the proportion of dry season runoff volume to yearly total runoff volume continuously increased after 30-years soil and water comprehensive management in Pingjiang watershed. The watershed sediment transportation decreased by 1.48% per year, especially during the later period from 2003 to 2015, 61.4% of the eroded sediment was trapped in the watershed compared with the value of period before management. The watershed soil and water comprehensive management show a significant positive effect in runoff distribution and sediment trapping.