The inclusion interaction between cocaine hydrochloride（CH） and p sulfonated calix［4］arene（SC4A） was investigated by fluorescence and 1H NMR spectroscopy.Influences of pH value,temperature,ionic strength and SC4A concentration were examined in detail.In pH 7.5 Britton-Robinson solution,the fluorescence of CH was dramatically reduced to quench upon the addition of SC4A,revealing the formation of inclusion complexes between CH and SC4A.The stoichiometric ratio was verified to be 1∶1 by the continuous variation method.The binding constant of CH-SC4A complexes was calculated to be 6.93×104 L/mol by the nonlinear curve fitting method.1H NMR spectra showed that the bridge ring moiety containing N—CH3 of CH may partially penetrate into the hydrophobic cavity of SC4A.This was confirmed by density functional theory calculations.