In this study, a small platinized tungsten coil (TC) with a composite structure was utilized for the first time in a liquid sampling electrothermal vaporizer (ETV) setup. A novel direct sampling mercury (Hg) analyzer coupled with a dielectric barrier discharge (DBD) and a miniature fiber optic spectrometer (FOS) as an optical emission spectrometer was fabricated for the sensitive determination of Hg in environmental water. This ETV setup displayed a maximum sample volume of 100 μL and fulfilled the task of sequestering Hg during the dehydration and ashing processes under high temperature due to the formation of a platinum (Pt) and Hg amalgam. Under optimized conditions, the limit of detection (LOD) of Hg was 0.1 μg L-1 for a 100 μL liquid sample and the relative standard deviation (RSD) of 11 repeated measurements of Hg standard solution was 3.2%; the linearity (R2) was > 0.999 in the range of 0.4-100 μg L-1. The results for the GBW08063 sample (9.89 μg L-1) agreed with the certified values of certified reference materials (CRMs) (10 μg L-1), and the spiked recoveries were 94-100%, which proved favorable analytical accuracy and precision. The total analysis time was observed to be less than 3 min, and this small-sized ETV-DBD-OES system consumes only ~100 W of power while weighting less than 12 kg. Therefore, the proposed ETV-DBD-OES method demonstrates simplicity, suitable sensitivity, precision, and robustness, with promising application in the field for rapid water analysis for Hg.