It is desirable for the next generation of supersonic transport (SST) to have not only better fuel efficiency but also less environmental impact. With an increasing concern over the environmental impact of aircraft, alternative fuels have risen in significance. For this reason, the authors have conducted a feasibility study on hydrogen-fueled SST. In order to evaluate the performance and environmental impact, an conceptual design environment of an integrated airframe-propulsion system was constructed. In this paper, the performances of hydrogen-fueled SST are compared with conventional kerosene-fueled one. Furthermore, the environmental impact including the impact on climate changes, the sonic boom, NOx emission and airport noise, are also discussed in detail.