Abstract A method for separation and determination of Cl −, NO 3 − and SO 4 2− in river water by capillary electrophoresis with indirect UV detection was described. A background electrolyte consisting of sodium borate, chromate and cetyltrimethylammonium bromide (CTAB) was employed for the separation. Methanol as additive was added to the system for improving separation selectivity of NO 3 − and SO 4 2− through adjusting the elution order of anions. High concentrations of SO 4 2− did not interfere with the determination of NO 3 − because SO 4 2− was eluted later than NO 3 −. The effects of the concentration of sodium borate and CTAB on separation were also examined. The detection limits of Cl −, NO 3 − and SO 4 2− were 1·10 −7 mol/l. The concentration of Cl −, NO 3 − and SO 4 2− in river water was determined quantitatively using NO 2 − as an internal standard. Standard addition recoveries of the Cl −, NO 3 − and SO 4 2− in the river water sample were between 89∼105%. The results were consistent with those obtained by ion chromatography.