An existing public building located in Jinan has been reconstructed using renewable energy according to the national energy conservation standard. The successful technology and experience used for energy conservation of existing building reconstruction in Sweden were used for reference in the design process of this building which to be reconstructed as energy saving building using renewable energy. The conservation performances of different renew-able energy adopted in this project were compared. Economical efficiency analysis for investment and economic benefit of energy conservation reconstruction with renewable energy for this building has also been made, which may be useful to the energy saving reconstruction using renewable energy for the existing public buildings in China.