Abstract: A method was proposed for simultaneous determination of arseniteAs(Ⅲ), arsenateAs(Ⅴ), monomethylarsenic acid (MMA), dimethylarsenic acid (DMA), seleniteSe(Ⅳ), selenateSe(Ⅵ) and Cr(Ⅵ) in fresh water by high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). A mixture of 20 mmol·L^-1 NH₄NO₃ solution (pH 8.7) and 60 mmol·L^-1 NH₄NO₃ solution (pH 8.7) in different volume ratios was used as the mobile phase for gradient elution. Seven element species were separated under the optimized chromatographic conditions within 14 min, and the chloride had no interference to ⁷⁵As, ⁷⁷Se and ⁵³Cr. Linear relationships of 7 element species were found in definite ranges, and the detection limits were 0.06 μg·L^-1 for As (Ⅲ), 0.02 μg·L^-1 for As(Ⅴ), 0.04 μg·L^-1 for MMA, 0.05 μg·L^-1 for DMA, 1.00 μg·L^-1 for Se(Ⅳ), 1.00 μg·L^-1 for Se(Ⅵ) and 0.20 μg·L^-1 for Cr(Ⅵ), respectively. Test for recovery was made by standard addition method, giving results in the range of 80.1%-101%, with RSDs (n=6) ranged from 0.59% to 5.2%.