The invention discloses a core/shell-type multifunctional nano material and a preparation method thereof. The core of the multifunctional nano material is an up-conversion nano luminescent material and the shell is an alkaline manganese compound, nano golden particles deposited between the core and the shell. The core/shell-type multifunctional nano material achieves fluorescence detection and magnetic resonance imaging analysis at the same time, wherein the core material is a rare earth up-conversion nano luminescent material, so that a fluorescent marking/imaging function can be achieved. The shell material is the alkaline manganese compound, which is decomposed into an MRI contrast agent Mn<2+> when the material enters a tumor cell, so that MRI imaging of the tumor cell can be achieved accurately. Meanwhile, the material releases the fluorescence up-conversion core material to achieve up-conversion fluorescence imaging. The nano golden has the photo-thermal effect and CT imaging function, so that when the material enters the tumor cell, the material not only achieves fluorescence/MRI double-function imaging but also achieves CT imaging and photo-thermal therapy.