The analysis method of 3-Monochloropropane-1,2-diol (3-MCPD) compound in water was developedusing liquid chromatography with mass spectrometric detection. Aqueous solution was controled in strong basiccondition with sodium hydroxide, and then 25 L of benzoyl chloride was added to the solution for thederivatization of 3-MCPD. The derivative was extracted using pentane and analyzed by the selected ionrange of 1.0 to 100 g/mL with a good linearity (correlation coefficient of r2 = 0.992) and limit of detectionwas below 0.01 g/mL. The recoveries of this analysis method by LC-MS were 92.3-98.0 %.