Amoxicillin (AMX) is a highly antibiotic resistance so that many studies focus on the removal of AMX in water environment. The present study investigated adsorptive removal of beta-lactam antibiotic AMX using a cationic surfactant, cetyltrimethylamonium bromide (CTAB) modified nanosilica (CMNS). The CTAB adsorption on nanosilica was independent of ionic strength, indicating that both electrostatic and hydrophobic interaction induced adsorption. Effective conditions for AMX removal using CMNS were systematically studied. The AMX removal using 10 mg/ mL CMNS reached 99 % at pH 9. Adsorption isotherms of AMX on CMNS at two salt concentrations were in good agreement with Langmuir model than Freundlich model. Adsorption isotherms at different ionic strengths and the surface modification by Fourier transform infrared (FT-IR) spectroscopy demonstrate that AMX adsorption on CMNS was mainly controlled by electrostatic interaction.