The invention discloses a novel method for generating electricity by pyrolysis and incineration of waste. The method comprises the following steps of: (1) urban household waste pretreatment; (2) waste gasification; (3) gasified gas purification; (4) gasified gas burning for generating electricity; and (5) sewage treatment and energy conservation. In the method, only clean combustible mixed gas and harmless ash are generated, and the two products have value in use; the mixed gas is a mixture which contains carbon monoxide, nitrogen, alkanes and hydrogen, can be used for generating electricity, and has higher electricity-generating efficiency compared with other waste treatment techniques; the carbon dioxide generated during burning the clean mixed gas is reduced greatly to minimize the influence on the environment; during the urban waste treatment, waste classification is not required; fuels except waste are not required; compared with electricity generation by burning waste directly, the novel method does not need expensive waste gas treatment systems, sewage treatment systems, boiler feed systems, matching systems for generating electricity, and the like, so the equipment investment is low.