Abstract: A typical large-scaled pig farm was selected to monitor the ground water quality. The results showed that pH，total nitrogen concentration and number of fecal coliforms was 7.72-7.79，1.73-2.87 mg/L and 3.663× 105-5.257×105，respectively，in the water of five wells，the number of fecal coliforms exceeded the standard level of ground water. Further investigations in well water quality were conducted on two typical wells. Results showed that the concentrations of nitrate nitrogen and total soluble solids were lower than class Ⅰ of water quality standard；the nitrite content was lower than class Ⅲ of water quality standard. The concentrations of total nitrogen and total phosphorus were 3.06-3.42 mg/L and 0.12-0.21 mg/L，respectively. The well water was polluted by some organic contaminants as evinced by the variations of COD and BOD5. Ammonia nitrogen and fecal coliforms were pollutants found in the water of two wells and were much higher than the class V of water quality standard. In summary，the water quality in this large-scaled pig farm was poor mainly because of the ammonium nitrogen and fecal coliforms contamination