Environment-friendly soybean planting system has been being required in the upland field with high slope and heavy rain in summer season. Changes of weed amount and soybean yield by rye cover crop and conservation tillage were investigated. Soil-disturbing at conservation tillage before soybean planting increased numbers and dry weights of weeds germinated in late spring such as Echinochloa crusgalli P. Beauv (barnyardgrass) and Portulaca oleracea L. (common purslane) regardless of herbicide spray even though the weed, Chenopodium ficifolium Smith germinated before soil-disturbing were higher at non-disturbing soil. Higher weed amounts at plots of strip-tillage (30cm rototilling) compared to minimum tillage (10cm rototilling) was mainly due to the weed increase by soil-disturbing. Soybean yields at plots with rye cover crop, particularly early maturity rye cover crop, were lower than those at plots without rye cover crop, which was due to lower soybean seedling stand by heavy rye residue. More researches are required for the higher soybean yield at the minimum tillage with rye cover crop in which weed amounts were low.