The five main factors influencing the deposition of uranium in hydrothermal uranium deposits are discussed in this article, which are temperature, static pressure, component of fluids( including gas and liquid) ,pH Value and Eh value, which are studied by experimental geochemical methods. Combined with the calculation of thermodynamics of gas in inclusions in minerals, the conclusions are: ( 1 ) pH value of the solution in the ore forming stage and pre-ore forming stage in the rich deposit decreased dramatically( △pH value is big). This effect is not obvious in the barren ore. (2)the value of fH2, fCH4 and αu are high which is 10-2 to 10-4 mol/1. (3)the solution is rich in Ca2+. The supersaturation degree is low. The temperature gradient is positive , the impurity in the solution is little which shows that the mineralization degree is low. (4) Decarbonization or escaping of carbon oxide can make the uranium deposited and the separation of uranium and silicon. (5) The environment of ore forming is relatively close and the ore forming temperature is relatively high, which is favourable for ore forming.%通过实验地球化学方法,得出影响热液铀矿床铀沉淀的5个主要因素:温度、静压力、流体成分、溶液pH值和溶液Eh值.利用矿物包裹体气体成分热力学计算对比,得出富矿床成矿期与成矿前的溶液pH值显著降低(△pH大);fH2,fCH4和αu较高(10-2～10-4mol/1);富含Ca2+离子;具较小过饱和度、正温度梯度、少杂质(矿化度小);适当脱碳酸或CO2(促使铀沉淀和铀硅分离),相对封闭稳定、成矿温度稍高的环境等是值得重视的对成矿有利的环境.
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