Here one demonstration project of groundwater heat pump (GWHP) system in Beijing plain, China, was selected to study impact of temperature, pH, and ratio of carbon and nitrogen in groundwater on the growth of microorganism. Results showed that pH, and ratio of carbon and nitrogen had little influence, while temperature played an important role. When temperature was higher or lower than 13.2 0 C, the amount of Escherichia coli and bacteria showed a decreasing trend roughly consistent with the normal distribution. Meanwhile, based on the monitored data, the relationship between groundwater temperature and the capacity of E. coli and bacteria were summarized.