Combinatorial laser MBE (CLMBE) method was employed to fabricate epitaxial ZnO thin films doped with all the 3d transition metal ions, The solubility behavior of 3d ions was studied from the viewpoints of ionic radius and valence state. Transmission spectra were classified into four groups with respect to the absorption edge shifts and d-d electron transitions. Mn2+ and Co2+ ions show very high solubility limits among all the 3d ion species and have high spin electron configurations in ZaO matrix. Such a high throughput synthesis tool as CLMBE is shown to be a powerful tool for exploring novel functionality of thin film materials.