Abstract: The complexation of some Coumarin derivatives(C_(311), C_(47), C_(102), C_(120) and C_4) With β-CyD in aqueous solution has been examined by means of steady-state and time resolved fluorescence methods. It is observed that the fluorescence peaks, relative intensities and lifetimes of the guest molecules in aqueous solution of β- CyD reveal hypsoehromic shift, enhancement and increment respectively relative to those of guest molecules in aqueous solution. The results indicate that the CNDs complex with β-CyD to a certain extent. The measured complexation constants for CND—β-Cye systems decrease in the order of K_311 K_47 K_102 K_120 K_4. These facts reflect that the hydrophobic property of guest molecule and the matching size between the guest molecule and β-CyD are important factors affecting their complexation.