Abstract: Based on the literature research, the investigation of the effect of β-cyclodextrin as mobile phase additive on the retention behaviour of methylphenobarbitone enantiomers under the chromatographic condition was made theoretically and experimentaly. The effecting factors on the apparant capacity factor k′ and /or stability constant K o f inclusion complex, such as concentration of cyclodextrin additive and solvent strength in the mobile phase, were also studied systematicaly。Through the linear regression of the experimental date, amathem atical relation between the stability constant of enantioselective inclusion complex and solvent strength in the mobile phase was obtained.