A magnetic solid phase extraction（MSPE） technique was developed by polymerizing methyl acrylic acid（MAA） on the surface of silica modified Fe3O4 magnetic nanoparticles（Fe3O4@SiO2@MAA MNPs）,which was combined with HPLC-MS/MS method to analyze the tobacco specific N nitrosamines（TSNAs） in mainstream cigarette smoke.In this method,TSNAs were enriched by adding magnetic nano particles to the extract.The separation was fast under the effect of magnetic materials.The eluent was detected by HPLC-MS/MS under multiple reaction monitoring mode,which could meet the requirements for detection of trace TSNAs in low tar and new tobacco products.The results showed that Fe3O4@SiO2@MAA MNPs had the uniform size,good monodispersity and super paramagnetism,on which surfaces the carboxyl functional groups could adsorb TSNAs in the solution for separation and enrichment.The pre treatment method was rapid and simple,and was suitable for analysis on samples of large quantities.The average recoveries for 4 TSNAs ranged from 883% to 1128% with the limits of quantitation（LOQs） of 010-048 μg/L.The method was suitable for the detection of TSNAs with low contents under the complex background.