Harmless treatment system and method for waste

The invention discloses a harmless treatment system for waste. The harmless treatment system for waste comprises a feeding system, a gasifier, a reforming separator, a secondary combustion chamber and a flue gas purification system which are sequentially connected, and further comprises a melting unit, a first waste liquid injection unit communicating with the gasifier and a second waste liquid injection unit communicating with the secondary combustion chamber, wherein the feeding system is used for feeding solid waste to the gasifier; the gasifier is used for gasifying the waste; the reforming separator is used for carrying out dust removal and reforming on gasified gas, the reforming separator is provided with a fly ash outlet and a reformed gasified gas outlet, the fly ash outlet is connected with the gasifier, and the gasified gas outlet is connected with the secondary combustion chamber; the reformed gasified gas is combusted in the secondary combustion chamber; and the flue gas purification system is us