Abstract: Objective Toidentify the possible infection source of one case of human infection with avian influenza A (H7N9) virus reported in Deqing, Zhejiang province, in January 2016, and provide scientific evidence for the prevention and control of avian influenza infection in human. Methods The case and his close contacts were surveyed, and external environment samples were collected for laboratory testing. Results The patient,aged 76 years, was confirmed to be infected with human avian influenza A (H7N9) virus, and eventually died despite the treatment was given. The case had history of hypertension. The case had exposure history to a farm produce market but no history of exposure to alive poultry within 7 days before onset. Although there were no alive poultry in the farm produce market, one polluted water sample was detected to be positive for H7N9 viral nucleic acid at a killed poultry stall. Positive samples of H7N9 viral nucleic acid were detected in poultry cages and slaughter sites in all of the three killed poultry stalls. No acute respiratory symptoms were found in the 13 close contacts of the patient. Conclusion It was highly possible that the case was infected in the farm produce market contaminated by H7N9 virus, indicating that health management and disinfection in farm produce market need to be strengthened, and poultry slaughtering and sale procedure need to be standardized.