Abstract: The sharp increase of peak load in summer has become an origin of power supply shortage.It may result in excessive grid reserve capacity,no-load loss increase of transformers and other equipment,and low equipment utilization by merely adding power supply and distribution equipment for resolving heavy overload of equipment. Based on the historical load and meteorological data in a region in south China,this paper analyzes the duration of peak load of power grid,air-conditioning load and composition of peak load industries in summer. The study shows that in this region the duration of summer peak load is short but the high load is constant in those peak load days; the summer peak load is mainly composed of residential air-conditioning load,and temperature is a major influencing factor of the summer peak load. Based on the above,optimization measures of peak regulation of local power plants and demand-side response are proposed.