To understand the heavy metals Arsenic speciation and influence factors in the water of Wuliangsuhai Lake, the samples were collected. The total Arsenic concentration was analyzed. As different chemical species in water have different toxity to organism, the speciation of the studied metals in WL was analyzed with the PHREEQC model. The impact of temperature, redox and pH on the heavy metal species in WL was simulated with the PHREEQC. The results showed that the average Arsenic concentrations in lake water were 6.67μg·L-1. All sampling contents were not beyond the surface water standards and national fisheries standards. The mainly chemical species of Arsenic in water solution were HAsO42, however, the N13 water sites were H3AsO3 which content is 97.59%. The change of temperature have minor impact on the speciation of Arsenic. pH influences greatly the speciation of Arsenic. In the condition of low pH (pH=6~7.5), the counter hydrolysis reaction of heavy metals is dominant. In the condition of high pH (pH=7.5~11), the hydrolysis reaction of heavy metals is dominant. Water redox condition in the lake has different effects on Arsenic speciation. In the reduction condition, H3AsO3, and H2AsO3- are the dominant species. In the oxidation condition, HAsO42-, and H2AsO4- are dominant species. So, for the cold lake, more attention should be paid to the icebound lake environment and water arsenic content.%为阐明湖泊水体中砷（As）的存在形态及水环境条件对重金属形态变化的影响规律，对湖泊重金属污染修复治理方面提供科学依据，采集乌梁素海水样，对湖水中As含量与存在形态进行分析，在考虑As污染程度的基础上，利用PHREEQC研究湖泊水体中As的存在形态，并分析温度、酸碱度及氧化还原条件对As存在形态的影响。结果表明，水样中As含量范围在2.27~11.98μg·L-1之间，平均含量为6.67μg·L-1（n=15，std=3.41），其所有监测点的含量都未超出地表水标准和国家渔业用水标准.水体中 As 的主要存在形态为五价态的 HAsO42-；N13采样点 As 的主要存在形态较为特殊，主要为三价态H3AsO3，含量达到97.59%。温度对 As 各种存在形态最终分布无大影响。As 存在形态受 pH 影响较大，水体 pH 较低时（pH=6~7.5），As主要以配合反应为主；随着pH的升高（pH=7.5~11），As逐渐发生水解反应。水体的氧化还原性对As影响较明显，当水体处于还原状态时，As主要以H3AsO3和H2AsO3-占主导地位；处于氧化性状态时，HAsO42-和H2AsO4-占主导地位。因此对于寒旱区湖泊，应对冰封期湖泊环境与水体砷含量予以重视。
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