Abstract: Drinking water quality for human health safety is the primary problem of water sources. Analysis and evaluation in this aspect were conducted on the basis of investigation of a tin pit water which serves as drinking water source of town A in Gejiu City and ore block B. Human health risk assessment of drinking water was carried out with the risk assessment model recommended by the International Radiation Protection Committee and the US Environmental Protection Agency. The results show that health hazards of carcinogenic material caused by heavy metals in water are high, and the risk value exceeds the maximum acceptable level of risk recommended by the International Commission on Radiological Protection. Sexavalence chromium and arsenic are maximum carcinogenic risk substances and hence should be preferentially controlled. The health risk caused by the non-carcinogenic matter is relatively insignificant. The values below 10-8 are by far lower than the recommended maximum acceptable risk level. Although the heavy metal content in water meets the requirements of relevant standards, there still exists human health risk if such water is drunk for a very long time.