A mathematical model concerning the separation selectivity of basic analytes in chiral capillary electrophoresis (CE) modified with negatively charged cyclodextrins (CDs) has been presented to describe the dependence of chiral selectivity on the buffer pH and the chiral selector concentration. The electrophoretic method to determine the parameters of the model has also been developed. The model has been tested with racemic epinephrine and isoproterenol as target analytes and sulfonated P-CD as chiral selector. The agreements have been found between the calculated and the measured values. Some significant conclusions to optimize chiral CE separation have been derived from the model and proven by the experiments. Electrochemical detection was used to meet the requirement of the low introduced concentration of analytes.