In our study, the development of amino functionalized carbon coated magnetic nanoparticles (NH2-CC-MNPS) and their usage for electrochemical detection of hybridization of nucleic acids have been aimed. Firstly, NH2CC-MNPS were prepared by coating of pristine Fe3O4 nanoparticles with two layers via caramelization and silanization processes respectively. After the morphological characterization with scanning electron microscopy (SEM) it was seen that NH2-CC-MNPs was spherical shaped and in 28 nm sized. Investigation of chemical composition with the help of scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and fourier transform infrared spectroscopy (FTIR) was showed incorporation of carbon and APTES to the structure of NH2-CC-MNPs. Magnetic property of NH2-CC-MNPs after two layered coatings was demonstrated with electron spin resonance (ESR) technique and gfactor was calculated as 2.6. In the second part of this study, optimization studies have carried out onto the surface of NH2-CC-MNPS prepared in saltless phosphate-tween 20 buffer (PBTw) for the analysis of DNA hybridization. The thiol linked DNA probe sequence representing to the Hepatitis B virus (HBV) concentration, target DNA sequence concentration, the most productive hybridization time and the selection of the nanoparticle surfaces have been researched. The electrochemical detection of DNA hybridization was investigated using PGE in combination with differential pulse voltammetry (DPV) technique by measuring the guanine oxidation signal. The detection limit was calculated in the linear target DNA concentration range of 5-25 rho/mL and it was found to be 1.15 mu g/mL (20 pmol in 110 mu L solution). It has been intended to be more reproducible, more sensitive and faster results with developed biosensor technology.