Abstract: The chloride lake brine generally has a higher concentration of sodium than potassium. The original sample was diluted step by step without any pre-treatment. A reasonable ratio of sodium to potassium standard solution series was prepared and the contents of potassium and sodium were directly determinated by atomic emission spectrometry under the optimized measurement condition. This method has been applied to the determination of sodium and potassium in chloride lake brine and the recovery was from 91% to 116% with the precision of less than 1% RSD(n=7).