Some hypotheses of the genetic mechanism of columnar joints in basalt a re introd uced and commented in this paper.In regard to the forming mechanism of columnar joints in basalt the hypothesis of doublediffusive convec tion is not in contradiction with the traditional hypothesis of coolingcontrac tion and they are mutually complementary, both elucidating from their respective approaches the forming processes and developmental characteristics of the initial fractures in basalt in various developmental stages, such as before and after the consolidation or rockforming of molten basaltic magma, and their c ausal relation.These hypotheses can be used to explain clearly the formation me chanism of columnar joints in basalt of the Guizi hill,Liuhe, Nanjing.