To achieve the secondary utilization of industrial waste, alkali-activated fly ash-slag composite gel material (AAFSC) was prepared by partially replacing fly ash with carbide slag and mixing it into alkali-activated fly ash-slag (AAFS). The carbonization resistance of AAFSC with different carbide slag content was investigated, and the microstructure of materials was analyzed by mercury intrusion porosimetry, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. The results show that after the rapid carbonization process, the pore structure of AAFSC develops towards harmful pores, resulting in a significant decrease in compressive strength after carbonization. Compared with AAFS, AAFSC exhibits superior carbonization resistance in the early and middle stage before carbonization. However, this advantage gradually decreases or even disappeares with the prolongation of carbonization age. AAFSC with 6% carbide slag content has the best carbonization resistance in the early and middle stage before carbonization and still has the maximum compressive strength of 39.92 MPa in the later stage after carbonization. With the increase of carbide slag content, Ca(OH)2 content in AAFSC increases, and these Ca(OH)2 are consumed during carbonization, resulting in the formation of calcite, aragonite and other carbonates.