The stable geometries, electronic structures, and magnetic behaviors of the ScLin(n= 2-13) clusters are investigated by using particle swarm optimization (PSO) and density functional theory (DFT). The results show that these clusters have three-dimensional (3D) structures except ScLi2, and ScLi12, and ScLi(13)that possess the cage-like structures. In analyses of the average binding energy, second-order difference of energy, and fragmentation energy, ScLi(12)cluster is identified as magnetic superatom. The magnetic moment for each of these clusters owns an oscillating curve of different cluster sizes, and their magnetic moments are further investigated using molecular orbitals and jellium model. Of ScLin(n= 2-13) clusters, ScLi(12)has the largest spin magnetic moment (3 mu(B)), and molecular orbitals of ScLi(12)can be described as1S21P61D alpha 5D beta 2<i. Additionally, Mulliken population and AdNDP bonding analysis are discussed and the results reveal that the Sc atom and Li(n)atoms make equal contribution to the total magnetic moment, and atomic charges transfer between Sc atoms and Li atoms.