According to the geometrics of ridge furrow,a formula for calculating the volume of individual shallow basin in various slopes was derived,and an optimum block space model was developed.This model suited various sloping fields. Through the examination on 2°,4° and 6° sloping fields with 3.6mm/min rainstorm by rainfall simulater in the ridge plots of optimum block space,they intercepted the rainfall of 54.8,50.4,and 42.0mm respectively,and were 18.4,19.9,19.7 and 49.4,44.6,39.9mm higher than that on the maximum block space and the open ridge respectively.Under the natural rainfall,the yield of soybean on 6° sloping field according to this model was 2 200 kg/ha,and was 22.3% and 36.8% higher than the check plots of the maximum block space and the open ridge.Therefore,the model is verified to be feasible and reliable.