The invention relates to a system for synergistically treating household garbage through a cement kiln. The system comprises a garbage storing, incinerating and flue gas treating system, a combustion air system, a peculiar smell gas treating system, a steam boiler and power generation system, a garbage leachate treating system, a garbage clinker and fly ash treating system, a fuel combustion system and a bypass gas venting system. A garbage incinerator and a cement clinker production line are combined well, a series of characteristics of high temperature, high stability, high-concentration alkaline material, long staying time and others of a cement burning system are used for performing harmless treatment on dioxin in garbage incineration flue gas, harmful elements in garbage clinker and fly ash, garbage leachate and peculiar smell gas in a garbage storage pit, influences on the environment can completely meet the national standard requirements, and the purposes that the household garbage is harmless, the volume is reduced, and the household garbage is recycled and environmentally friendly are really achieved. The processes are simple, operation is easy and convenient, running is stable, and investment is small.