Carbide slag (CS), as a kind of industrial waste slag with high alkalinity has low comprehensive utilization rate. In order to solve the problem of excessive carbide slag, the alkali excitation performance of carbide slag on slag cementitious system was studied by using the strong alkaline of carbide slag. Based on the characteristics that carbide slag carbonization reaction generated calcium carbonate, the influences of different carbonization systems on the performance of alkali-activated slag cementitious system were explored. The results show that CS with large dosage has a good alkali-activated effect on the slag cementitious material, and a large amount of C-(A)-S-H gel is generated. The cementitious material with fly ash and metakaolin has best performance. The mechanical properties of carbide slag-slag composite material can be effectively improved after being treated by different carbonation systems. CO2 gas using as the external carbonation source leads to dense structure on the surface of material matrix, while urea as internal carbonization source makes the internal carbonation of matrix uniform, which improve mechanical properties of the carbide slag-slag composite cementitious material.