In order to optimize the optical properties of Au nanoclusters (NCs) a nd broaden their applications in various fields,ultrastable bimetallic fluorescent ZnAu NCs were prepared by atom-doped chemical method.Some characteristics and analysis,such as,UV-vis absorbance spectra,emission spectra,infrared spectra,fluorescent lifetime and so on,were conducted to stu dy the optical properties of ZnAu NCs and discuss the effect of Zn atom doping on the fluorescent intensity o f Au NCs.The structural properties of the bimetallic ZnAu NCs were analyzed by means of transmission ele ctron microscope (TEM) and mass spectrometry.Finally,the cytotoxicity assessment and cell imaging for ZnAu NCs were conducted to explore the applications in biomedicine for ZnAu NCs.The res ults indicate that as-prepared ZnAu NCs exhibit three-time fluorescence enhancement compared with the undoped Au NCs,and the fluorescent lifetime increases from 6.73μs to 7.26μs.Besides, the mass spectrometry investigations show the ultrasmall ZnAu NCs are complex clusters with molecule w eight of 5.0－5.8kDa.Due to excellent photostability and negligible cytotoxicity,ZnAu NCs have more promising applications in biomedical imaging.Meanwhile,Zn atom doping improves the fluore scent properties of Au NCs,providing more possibilities for their wide applications in other fields.