Shanghai has a certain amount of historic buildings, these building envelopes’ insulation performance is poor, in addition, they often use room air conditioners, and the energy consumption for air conditioning is high. In the paper, a typical small-scale historic building in Shanghai is assumed, the energy-saving potentials of several retrofitting measure is studied by hourly simulation for a whole year, the potentials several measures include addition of insulation to the external walls and roof, replacing the old windows with new type windows, air-conditioning by air-source heat pump or ground source heat pump system, the annual energy consumption and maximum heating and cooling load is calculated for each case, then some advice on retrofitting on historic buildings will be given.