Disclosed is a preparation method of a Au@Co(OH)2 nano-microsphere with a core-shell structure. Aurum nano-clusters (Au NCs) are adopted by the Au@Co(OH)2 nano-microsphere to serve as the core; and on the basis of the mechanism that abundant histidine on Au NCs surface stabilizer bovine serum albumin (BSA) can conduct chelation with Co<2+>, Co(NO3)2 solutions are repeatedly and slowly added to a Au NCs solution, ammonium hydroxide serves as a complexing agent, a Co(OH)2 shell layer is deposited on the surfaces of the Au NCs through a liquid-phase chemical precipitation coating method under the weakly alkaline condition, and the Au@Co(OH)2 nano-microsphere is obtained through preparation. The preparation method is gentle in reaction condition of Au@Co(OH)2 nano-microsphere preparation and high in repeatability, and has the potential application value of serving as a near infrared fluorescence-magnetic resonance bi-modal imaging probe.