Cotinine, Codeine, 1,7Dimethylxanthine and Caffeine are widely used in daily life as drugs and their metabolites. The stimulant residues in the environment may pose a threat to human health and ecological environment safety. Water samples were sampled under acidic conditions (0.1% formic acid aqueous solution) and the residual chlorine was removed by adding sodium thiosulfate (1 L water sample with 0.1 g sodium thiosulfate) to the water samples. Online solid phase extraction followed by LCMSMS was used to determine 4 stimulants in drinking water, including Cotinine, Codeine, 1,7Dimethylxanthine and Caffeine. When the injection volume was 1.0 mL, the detection limit of this method was 0.633～1.75 ng/L, the low limit of determination was 2.53～6.98 ng/L and the recoveries of standardadded drinking water samples ranged from 80.0% to 129%.The method has low detection limit and high recovery, and can meet the requirements of the daily detection of four stimulants in drinking water samples.