The invention discloses a device and a method for treating garbage fly ash into a cement raw material. The device comprises a cement kiln, an offline spouting furnace, a fly ash conveying device and a separator, wherein the fly ash conveying device is used for conveying garbage fly ash to the offline spouting furnace; the offline spouting furnace is used for treating garbage fly ash through hot air introduced out from the cement kiln and used for separating fly ash granules from dioxin in the garbage fly ash; the fly ash conveying device is used for separating air with the fly ash granules and dioxin into fly ash granules and air with dioxin, used for outputting the fly ash granules from an ash discharge tube of the separator, and used for outputting the air with dioxin to the cement kiln from an exhaust tube of the separator; the cement kiln is adopted for high-temperature combustion of dioxin in the air with dioxin. Compared with a conventional wet-method process, the device has the characteristics of simple procedure, low energy consumption and low treatment cost, and as a relatively small amount of water is used in the device, a certain water resource can be saved.