Based on DFT-GGA calculations, we investigate systematically the structural, electronic and magnetic properties of ComAln (m+n ≤ 6) clusters. The calculated results show that the most stable structure of ComAln (m+n ≤ 6) clusters prefers to form the maximized number of Co–Al bonds, and is more similar to the most stable structure of pure cobalt clusters. With increasing Al atom numbers, the average magnetism of the clusters is reduced linearly. The magnetism of the ComAl (m=2–5) clusters is 4 μB smaller than that of Com+1 clusters, this agrees well with the recent Stern-Gerlach's experimental result of magnetism detection for a larger size of CoNAlM cluster. Reduction of the magnetism of ComAln clusters is mainly attributed to the non-magnetic Al element embeded and the weakening of spin polarization of the Co atoms.