In this study，ascorbic acid was added into the sample solution to improve the signal intensity of Hg determined by inductively coupled plasma mass spectrometry(ICP-MS).Factors effecting the signal enhancement，such as concentrations of nitric acid and ascorbic acid，temperature and time of water bath，were optimized.According to the results，5% of HNO3，500 mg?L-1 of ascorbic acid and a 50 ℃ water bath for 20 min resulted in the highest sensitivity for Hg.A nearly 30 times signal enhancement factor could be achieved,and the detection limit of Hg was 1 ng?L-1.The calibration curve had a good linearity in the concentration range of 0.005-10.0 μg?L-1 with correlation coefficients above 0.999.The repeatability of the proposed method was obtained at 0.1 μg?L-1 of Hg2+ with the relative standard deviations（RSDs） of 5.6% by seven replicates.Besides，the mechanism for signal enhancement was investigated and discussed.