Agriculture land is expected to serve as food production and carbon (C) sequestration. No-tillage system is focused on one of the conservation management, which is less human alteration to the soil except for seeding. Therefore at the no-tillage system, soil C increase due to decreasing aeration by tillage and increasing aggregates that contain more C compared to conventional management. Our study was conducted to assess the changes in soil C accumulation and soil structure in the no-tillage management after conversion from conventional managements; soil C, bulk density, aboveground plant biomass and litter accumulation were measured. During 0 to 17 years after conversion from conventional to no-tillage system, where soil C concentration had increased at soil depth of 0-5 cm, and soil C storage tended to increase at soil depth of 0-25 cm. Soil C concentration and bulk density were negatively correlated, and aboveground plant biomass increased. These results indicate that rising soil C concentration and changing soil structure at the no-tillage system were due to increasing C input of aboveground plant, slowing litter decomposition and restricting soil respiration by less disturbance compared to conventional management.