Abstract: A method for simultaneous determination of nitrobenzene, aldehyde and ketone compounds in water samples by gas chromatography with pre-column derivatization was developed. Parameters affecting the derivatization efficiency, such as pH, reaction time and temperature, dosage of derivatization reagent of 2,4-dinitrophenylhydrazine (DNPH) were tested and optimized. The optimum derivatization condition was set at pH=3 and 40℃ for an hour in a water bath. The reaction products of hydrazone and nitrobenzene compounds were extracted with dichloromethane, concentrated by rotary evaporator and converting the system to methanol medium by nitrogen-blowing. And then the target compounds were determined by gas chromatograph with electron capture detector. The detection limits of the method for organic components were in the range of 0.01~0.03 μg/L and the correlation coefficients of the calibration curves for the analytes were between 0.9989~0.9998. The recoveries were 89.5%~110.0% with precision of <6.0% RSD (n=6). The method provides the advantages of high recovery, high efficiency, economy, simple operation and is suitable for routine analysis of nitrobenzene, aldehyde, and ketone compounds in water samples.