The present invention discloses a superparamagnetic iron oxide nanoclusters and a preparation method and an application thereof. The superparamagnetic iron oxide nanoclusters are synthesized 5 by an improved solvothermal method, ferric chloride hexahydrate (FeC1306H20) is used as a raw material, a cluster-shaped product Fe304 is synthesized by a hydrothermal method, and a size of the cluster-shaped product Fe304 is adjustable within a range of 60-200 nm by changing a proportion of a mixed solvent. Because of characteristics of good biocompatibility, unique magnetic characteristic, pH response and the like, the superparamagnetic iron oxide nanoclusters prepared by 10 the present invention not only can be used as a Magnetic Resonance Imaging (MRI)-T2 weighted nanoprobe for magnetic resonance molecular imaging, but also has the characteristic of pH response.
