Abstract: The present invention relates to water soluble magnetic nanocomposite using an amphiphilic compound. Specifically, the present invention relates to water soluble magnetic nanocomposite which may be not only used as a contrast agent for magnetic resonance imaging (MRI), an intelligent contrast agent for diagnosing cancer characterized by binding a tissue-specific binder ingredient, a drug delivery system for simultaneous diagnosis and treatment by polymerizing or enveloping drugs and binding a tissue-specific binder ingredient, but also used for separating a target substance using magnetism, and a process for preparing the same.