Combined with the actual utilization of sloping farmland in the black soil area of Northeast China, surface runoff and soil loss from natural slope under natural rainfall condition were monitored and the benefits of soil and water conservation and their dominant driving factors were analyzed for three different soil tillage systems on 5° and 8° sloping farmlands of dark brown soil. Results showed that:(1) Surface runoff was greatly affected by soil tillage systems in corn field. These tillage systems were in the order of 8° ridged cross slope> 8° ridged cross slope with straw returning> 5° ridged cross slope> 5° ridged cross slope with straw returning> 8° ridged cross slope with straw returning and field bund with plants> 5° ridged cross slope with straw returning and field bund with plants. (2) The trends of runoff and sediment from different plots were similar, i.e., the more runoff, the larger sediment, but no line relationship appeared. (3) The largest runoff was found in the plot of 8° ridged cross slope. I₃₀ could be used to determine whether surface runoff occurred or not. There was 91% probability of runoff yielding when I₃₀ ≥ 6 mm/30 min, and the minimum rainfall for runoff yielding was 6 mm. (4) Rainfall intensity, not rainfall amount, greatly affected whether or not runoff occurred in the two plots of 8° and 5° ridged cross slope with straw returning and field bund with plants.