Trihalomethanes (THMs) are the result of the reaction between chlorine and organic matter in the chlorination process of water. Measurement of this compound in water is necessary due to the possible risks to human health. In this study, direct aqueous injection (DAI) using a gas chromatograph equipped with a pulsed discharge electron capture detector (PDECD) was used to analyze the THMs. The results showed that there is a significant linear relationship between concentration and peak area up to a concentration of 300 μg/L for THMs (chloroform, bromodichloromethane, dibromochloromethane and, bromoform). The limit of detection (LOD) was obtained 4.2, 4.0, 4.3 and 5.3 μg/L. Without any preconcentration of samples, small quantities of LOD values indicate the proper sensitivity of the detector and the analysis method. As a result, instead of the common type of electron capture detector (using 63Ni), pulsed discharge electron capture detector can be used.