This paper introduce the possibility of the city energy shortage in the summer and dealing with the emergency cases with the gas-electricity peak shaving method to ensure security energy supply of city in accordance with distributed energy system (DES), such as the gas turbine power generation central heating and cooling technologies. Simultaneously, this paper explain the feasibility of gas fired of heat, cold and power cogeneration system in building through typical example of model project and give some suggestions of energy supply emergency response system in the main city with a diversified city energy system.