Two novel tetranuclear lanthanide compounds with the formula [Ln4(L1)2(L2)2(μ2- OCH3)2(CH3OH)2]·CH3OH (Ln = Gd (1), Dy (2), H2L1 = 2-[(2-(hydroxyimino)propanehydrazide)methyl]-8-hydroxyquinoline, H3L2 = 2-[(2-(N'-acetylhydrazino)propanehydrazide)methyl]-8-hydroxyquinoline) were successfully prepared, and structurally and magnetically characterized. Crystal structural analyses reveal that two compounds are isostructural and they all consist of a tetranuclear Ln4 cluster. All Ln(III) ions in them are eight-coordinated and located in a distorted triangular dodecahedron geometry. Magnetic studies indicate that 1 exhibits large magnetocaloric effect with the entropy change (-ΔSm) of 32.10 J Kg−1 K−1 (at T = 2.0 K and ΔH = 7 T), and 2 displays slow magnetic relaxation behaviors.