Abstract: The mechanism of enantioselectivity in cyclodextrinmediated capillary zone electrophoresis (CD-CZE) on basic drug tulobuterol was discussed. The equilibrium constants of hostguest complexion of tulobuterol enantiomers with α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, 2,6-dimethyl-β-cyclodextrin, 2,3,6-trimethyl-β-cyclodextrin and 2-hydroxy-propyl-β-cyclodextrin, and the thermodynamic parameters for chiral recognition procedure were determined respectively. Selectivity calculated from the ratio of binding constants of two enantiomers is found to be in the same order of maximum electrophortic mobility difference between the enantiomers responding with cyclodextrin additive. The experimental value of optimal concentration of cyclodextrin agrees with the one calculated from Author the equation C_opt=1/(K₁K₂)^1/2.