According to the result of soil erosion rate depends on the different slope of bare land, we have obtained data as follows, (measured; June, 1966- October, 1966. Precipitation: 1094.5mm soil texture: sandy loam) The runoff was 552.1 ton in the 50 slope land 536.6 ton in the 10° slope land and 447. 8 ton in the 15° slope land per 10 a. i. e. the higher up degree of slope land goes, the less runoff becomes. On the contrary, the soil loss was 4. 8 ton in the 5° slope land, 16. 5 ton in the 10° slope land and 29. 7 ton in the 15° slope land per 10 a. i. e. the more higher up degree of slope land goes, the more soil loss becomes. According to the comparison test between the method of soil erosion Control by diversion drainage and of soil erosion control by grass strip which has occupied wide area as grass strip than that of diversion drainage in a condition of same cultivation area and guided it to farmers from 1959 to 1963 in Korea. As the runoff was 275 ton in the grass strip plot and 345 ton in the diversion drainage plot per 10 a. The former was less 71 ton than that of the latter. But the soil loss was 1.24 ton in the grass strip plot, 1.13 ton in the diversion drainage plot per 10 a. i. e. the former was more 0.11 ton per 10 a than that of the latter. Area of crop strip corresponds to 75% of the plot area carea of grass strip corresponds to 25% of the plot area) and to 95. 5% of the plot area in that of (Area of diversion drainage corresponds to 4. 5% of the plot area) strip. These indicated that the yield of diversion drainage plot was more increased to than that of grass strip plot by decreasing of practical crop’s planting area. Size and spacing of diversion drainage are different by soil texture and method of cultivation etc. Generally, it should be followed by next standard method. In case of contour farming, tardy slope and planting crop for soil conservation, the spacing must be limited to maximum 30-35 m. The spacing besides above mentioned circumst ance takes size below the 25 m in general, Spacing of diversion drainage(meter) Section area(㎤) of diversion of drainage x 5-Maximum mean precipitation per one year measured during 20 years.