In this research, formation and structure evaluation of optimized slurry aluminide coating by applying a pre-coating of Ni/Ni-Co electroplated layer on Ni-base superalloy were studied. First, some pure Ni and Ni– 45Co (at. %) layers were deposited on Ni-base superalloy, Hastelloy-X, samples separately by electroplating process at the specified conditions and 22-23 μ m thickness. Subsequently, the slurry aluminizing process was carried out on the pre-plated and a not-plated samples via the specified heat treatment. The obtained coatings with 142-148 μ m thickness were investigated by X-ray diffractometer and scanning electron microscope equipped by energy-dispersive X-ray spectroscope, and elemental mapping. According to the obtained results, β-NiAl desirable phase in all three samples and β-CoAl in the Ni-Co pre-plated sample were formed, definitely. The pre-plated layer reduced the diffusion of Cr and Fe, up to 4. 5 times of magnitude and Mo, up to 2. 5 times of magnitude to the upper parts of coatings by forming a diffusion barrier state. Present Ni in the pre-plated layer decreased the consumption of present Ni in the substrate alloy, too. Accordingly, the composition of substrate alloy in the pre-plated samples was less affected by diffusion coating process. Also, the present Co in the pre-plated layer of the Ni-Co pre-plated sample increased its amount, up to 7 times of magnitude in upper parts of the coating. This subject improved the possibility of formation of cobalt aluminide phases which confirmed by the formation of β-CoAl in upper parts of the coating.