The invention relates to a method and a device for treatment in feeding household garbage into a cement kiln in three routes. The method comprises the following steps: preparing the household garbage into high calorific value combustible refuse derived fuel, low calorific value combustible refuse derived fuel and inorganic materials a classified way; directly feeding the high calorific value combustible refuse derived fuel into parts such as a decomposing furnace, a kiln head combustor and a third air tube of the cement kiln to be combusted; after pyrolysis and gasification, feeding the low calorific value combustible refuse derived fuel into a decomposing furnace of the cement kiln in a form of fuel gas or caloric content; combusting the high calorific value combustible refuse derived fuel and the fuel gas fed into the decomposing furnace and the third air tube under the action of third air of a cement kiln system so as to completely combust combustible materials to release the heat; feeding the inorganic materials into a raw material system of the cement kiln. The method and the device have the beneficial effects that refuse fuel with different heat values can be treated without being limited by treatment scale, the fuel applicability is wide, the utilization rate is high, no waste slag is generated, and the operation is simple.