Abstract: Objective To describe characte ristics of hemag glutin in(HA) viral nucleic acid in live poultry markets in Pearl River Delta and to analyze potential risk factors of influenza Avirus epidemic.Methods From May 2007 to April 2008, we conducted a survey in 42 live poultry markets in Pearl River Delta.Standard questionnaires were adm in istered to market operators to collect information on market, types of birds and other an mials in the markets, and cleaning and disinfecting practice.The market was visited every month and was sampled at least 4 wipes from cage surface, ground, and ditch water.All samples were tested for vira l nucleic acid of influenza A virusby real time PCR.Risk factors were analysed for higher HA(influenza A virus) test rate.Results HA was identified in 876 of 3864 samples tested with a positive rate of 22.67%.There were positive detections for all 7 cities with positive rates of 7.23%-32.20%.There were positive results in every month with higher positive rates from September to February than average positive rate.The positive rate related to duck was 37.53%, higher than other animals.The factors associated with higher positive rate than average included marke tlocation in town(oddsratioOR=9.37, 1.07-82.35), retail transaction(OR=1.37, 1.08-1.73), and slaughter in the market(OR=1.37, 1.08-1.73).Conclusion HA viralnucleic acid can be detected in live poultry markets.Marke tlocation in town, retail mode, slaughter in the marke tare risk factors for high positive rate.