Abstract: As an important drinking water source in China, the causes analysis of groundwater pollution is of great significance for ensuring the safety of drinking water quality. Taking Qiqihar City as an example, statistical methods were used to analyze groundwater quality and pollution causes through four steps: data acquisition, evaluation index screening, water quality evaluation and cause analysis. The following conclusions were drawn: the groundwater quality in some parts of Qiqihar City was very poor, mainly due to excessive concentration of iron and manganese (Class Ⅲ water quality of the Quality Standard of Underground Water (GB/T 14848-2017)), and the phenomenon of excessive iron and manganese of the submersible water were more serious than that of the confined water. The high value area of iron concentration was mainly distributed in the central city and Tailai County, with the maximum exceeding the standard by 54.67 times. The high value area of manganese concentration was mainly distributed in the central city, Tailai County and Keshan County, with the maximum exceeding the standard by 15.40 times. The concentration of iron and manganese exceeding the standard was mainly related to the original geological conditions, and iron and manganese in the confined water was also related to the high mining intensity of groundwater in the area. The excessive concentration of iron in the groundwater was mainly correlated to pH, organic matter and ammonia nitrogen concentration, while the concentration of manganese was mainly correlated to pH of the groundwater and the dissolved ions concentration.