To determine the reaction ability of silicate aggregate in cementitious material，the optimum parameters of alkali-fusion of basalt were obtained by the orthogonal experiment. XRD and FTIR analysis were conducted to analyze the basalt of alkali fusion products，and the effect of the process and parameters of alkali fusion on the activated alumina content of basalt vitreous was researched. The results showed that the alkali fusion process could effectively improve the reactivity of basalt. The reactive phase content increased from 5.60% to 45.32%，and the content of reactive aluminum increased from 3.73% to 12.33% at most；The content of NaOH was a significant factor affecting the effect of alkali fusion；The activity of alkali fusion basalt increased with the increase of NaOH content. Chemical analysis for basalt activity improvement was related to the fracture of Si—O—Si and Al—O— Si bonds and the formation of[SiO₄ ]- and[AlO₄ ]- monomers during alkali fusion.