The strategy of "complex as ligand" allowed us to synthesize three new l-oxalato-bridged heterotrinuclear complexes identified as [Cu2Cr(ox)3(Mephen)2]ClO4 (1), [Cu2Fe(ox)3(Mephen)2]ClO4 (2) and [Cu2Fe(ox)3(Me2bpy)2]ClO4 (3), where ox represents the oxalato dianions; Mephen and Me2bpy stand for 5-methyl-1,10-phenanthroline and 4,40-dimethyl-2,20-bipyridine, respectively. The three heterotrinuclear complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, molar conductivity and magnetic moment (at room temperature) measurements, IR, ESR and electronic spectra studies, it is proposed that these complexes have an oxalato-bridged structure consisting of two copper(Ⅱ) ions and a chromium(Ⅲ) or an iron (Ⅲ)ion, in which the chromium(Ⅲ) or iron(Ⅲ) ion has an octahedral environment, and the two copper(Ⅱ) ions have a square-planar environment. Variable-temperature magnetic susceptibility (4.2-300K) measurements of the complexes 1 and 2 revealed the occurrence of an intramolecular ferromagnetic interaction between the copper(Ⅱ) and chromium(Ⅲ) ions for 1. On the other hand, the spin-coupling between the copper(Ⅱ) and iron(Ⅲ) ions through the oxalato-bridge in complex 2 is an antiferromagnetic. The magnetic data have been also used to deduce the indicated heterotrinuclear structure. On the basis of the spin-Hamiltonian, H=-2J(SCu1•SM+SCu2•SM) (M=Cr3+ or Fe3+), the magnetic analysis was carried out for the two complexes and the spin-coupling (J) was evaluated as +14.9cm-1 for 1 and )12.7cm-1 for 2.