Increasing sensibility and dectection limit in analysis of chlorinated organic compounds, especially dioxines, Polychlorinated Biphenyl (PCBs), are always focused by vanous international and national studies. In this paper, the analysis of Polychlorinated Dibenzo Dioxin (PCDDs), Polychlorinated Dibenzo Furan (PCDFs), and some Polychlorinated biphenyls (PCBs) by highresolution gas chromatography (HRGC) coupled with low resolution mass spectrometry (LRMS) is presented. Electron impact (EI), negative chemical ionization (NCI) mass spectrometry and Micro ECO detector were used. The method using HRGC and mass spectrometry was applied to analyze specific isomers of soil samples from Bien Hoa airport and the used transformer oil. Results of using NCI, EI and Micro ECO detector techniques were compared and shown that NCI increased sensibility to all PCDFs, PCDDs and PCBs except for 2,3,7,8 TCDD. This research indicated that this technique with combination of NCI and EI can be used to increase efficiently both of the sensibility and accuracy in analysis of PCDFs, PCDDs and PCBs.