In this paper,a method of surface enhanced Raman spectroscopy(SERS) based on core shell Au@Ag nanoparticles(Au@AgNPs) was developed for the rapid detection of famotidine(FMD).The Au@AgNPs were synthesized by seed growth method,and then characterized by SEM,TEM,UV-Vis spectrometry and XRD.Rhodamine 6(RG6) was used as the molecular probe to evaluate the SERS performance of Au@AgNPs.The synthesized Au@AgNPs has a uniform morphology and a good enhancement effect,with an enhancement factor of 6.66×105.The Au@AgNPs were used for SERS detection of FMD standard solution.Results showed that there was a good linear relationship between logarithm of concentration and logarithm of FMD peak intensity at 1 540 cm-1 in the range of 0.5-50 μmol/L,with a correlation coefficient(r2) of 0.978 and a detection limit(LOD) of 4.18×10-8 mol/L.Under the same conditions,Au@AgNPs were used for SERS detection of FMD in diluted plasma,with a LOD as low as 1.11×10-7 mol/L.The spiked recoveries were in the range of 91.6%-122% with relation standard deviations of 6.6%-12%.The experimental results demonstrated that this method is fast and sensitive,and has a potential application value in detection of biological sample.