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Although classical silver nanospheres were widely used as the probes in surface-enhanced Raman spectroscopy (SERS), they lacked long-term stability. In the present work, the silver nanoparticles decorated with β-cyclodextrin (β-CD-AgNPs) were used as the probe and the stability was improved. The adsorption characteristics of 6-mercaptopurine (6-MP) on classical silver nanospheres and β-CD-AgNPs were studied cautiously using SERS, and chemical information of the molecular structure was obtained. The binding of 6-MP molecule to the surface of AgNPs is based on the stable Ag-S covalent bond. The electrostatic adsorption between protonated N 7 atom or N 1 atom and the silver surface results in a notable Raman enhancement. The intensity of the Raman band of 6-MP at 866 cm −1 was used to determine 6-MP. The experimental conditions, such as volume of CD-AgNPs solution, incubation time, pH value and concentration of sodium chloride were examined and optimized.Compared with classical silver nanospheres when β-CD-Ag nanoparticles were used, the sensitivity was higher, the analytical time was shorter, and the linear range was wider. A good linearity (r=0.996) in the range of (0.040-2.0) ×10 -7 mol·L -1 was obtained for determining 6-MP. The limit of detection is 0.024×10 -7 mol·L -1 and the limit of quantification is 0.080×10 -7 mol·L -1 . This method was successfully applied to the determination of 6-MP in real samples and the results were satisfactory.