Traditional C18 solid-phase extraction material is prepared in chemical bonding method, which usually features in rigor conditions and complex process. It is an urgent issue in the field of chromatography to seek for a synthesis method featuring in simple preparation process and mild reaction conditions. SiO2@Ag composite particles were fabricated successfully in self-assembly method. This acquired core-shell composite particles were characterized with X-ray diffractometer (XRD), scanning electron microscopy (SEM) and Fourier infrared absorption spectrometer (FT-IR). N-Octadecanethiol (C18) was selected to modify the surface of composite particles in self-assembly method, then C18 solid-phase extraction material was obtained and named as SiO2@Ag-C18. Adsorption properties of this filler was studied with Benzo(a) pyrene as object of enrichment, so as to investigate adsorption-desorption cycle 20 times of SiO2@Ag-C18 characterized with energy dispersive spectroscopy (EDS) and stability of adsorption performance. Adsorption equilibrium was realized in 10 min and the maximum adsorption capacity was 15.49 mg/g at 32 ℃. C18 solid-phase extraction material is successfully prepared in self-assembly method featuring in mild conditions and simple process. SiO2@Ag-C18 exhibits good adsorption performance to benzene, and both its composition and properties are very stable.