Herein, a series of light lanthanide-based complexes, Ln(fdh)3(bpy) (Ln = CeIII, PrIII, and NdIII and fdh = 1,1,1-fluoro-5,5-dimethyl-hexa-2,4-dione, bpy = 2,2'-bipyridine), were synthesized and characterized. The angle-resolved magnetometry studies reveal that the three complexes have Ising-type anisotropy, and the magnetic easy axes orient along the negative charge dense direction in the crystal field. The results were consistent with the ab initio calculations. This research demonstrates that the crystal field electron density distribution determines the anisotropy of light lanthanides.