Abstract: Objective To study the epidemic characteristics of influenza, and establish the defending system for preventing influenza effectively. Methods To proceed the epidemiological observation with the outpatients who took the breath infection, adopt the embryonate chicken egg's double cavity method to isolate influenza virus and determine the crowd's antibody level with microplate hemagglutination inhibition (HI) test. Results No influenza virus was isolated in 1999 and 2000, but 12 strains of influenza A1(H1N1) in 2001.The highest positive rate of subtype A3(H3N2) was 79.25%(GMT62.78) in 1999,and the highest positive rate of subtype A1(H1N1) was 88.68% (GMT79.42) in 2000,and the highest positive rate of subtype A1(H1N1) was 76.40% (GMT54.28) in 2001. Of the two series of Btype influenza,only one series antibody appeared in the locate crowd,the other series weren't found in the local younger crowd.Conclusion In 2001,A1(H1N1) influenza occurred,and A1 type influenza virus antibody level was higher.If there was no antigen variation,A1 type influenza was not likely to soread.But A3(H3N2) and B type influenza virus antibody level was lower,and should enhance to defend.