The invention discloses a method for cycle power generation by treating garbage, which is rapid, residue-free, clean and innoxious and in particular can effectively prevent dioxins from synthesis. In the method, after being subjected to wet decomposition, dechlorination, debenzolization, dehydration, deodorization, sterilization and organic matter expansion, the domestic garbage is pyrolyzed by afurnace for pyrolysis, dry distillation and gasification, and the hydrogen-containing biomass gas generated after pyrolysis, cooling and purification is used for power generation by adopting gas turbine-steam turbine hybrid power generation technology. The invention has the following advantages: the domestic garbage is fully treated, no secondary pollution is produced in the treatment process, source control is carried out on synthesis of such toxic substances as dioxins and the like, and the power is the clean energy in the true sense; therefore, the method can completely replace the incinerator-steam turbine power generation technology which is largely adopted at present.