The present invention relates to a maghemite nanoparticle of which a surface is directly coupled to a compound and a preparation method thereof, wherein in a preparation process, the maghemite nanoparticle is maintained with stability for a long period of time in an aqueous solution, and can be coupled to a compound having a biologically active effect to maintain stability of maghemite and provide a pharmacological effect at the same time. Therefore, according to the present invention, the maghemite nanoparticle can be used for various fields such as bio, medicine and medical supplies, a medical device, an analysis instrument, or the like.