The result of survey on situation of poultry trade and surveillance on prevalence of A/H5N 1 virus at 4 wholesale markets in Hanoi city indicated that: Out of 4 above mentioned markets, Ha Vy market was the largest poultry wholesale market and the rate of poultry at this market coming from the outside of Hanoi city was also highest compared to the rest markets (North Thang Long market, San market and Chuc Son market). Close management on disease inspection and slaughter control works was paid by the competent authorities at these markets. In all of 4 markets, the average prevalence rate of A influenza virus was 11.28 percent. Of which, the prevalent rate of A/H5N1 virus was 2.54 percent. In general, the development of A influenza virus prevalence was stable in the last many years. The highest prevalent rate was usually occurred in duration from December to May of the next year. The prevalence of A/H5N1 virus at 4 markets was 1.11 percent (in 2009), 0.31 percent (in 2012) and 0.17 percent (in the first 6 months, 2013) having close relation with the origin of poultry coming from, vaccinated and protective rate after vaccination. The prevalence of A/H5N1 virus at 4 markets concentrated from January to May, that is time for the highest transportation and consumption of poultry (before and after Tet holidays) and the transition time for the first A/H5N1 vaccination in the year.