ObjectiveTo study the efficacy and safety of domestic oseltamivir phosphate in the treatment of patients during pandemic influenza A (H1N1) outbreak.MethodsAmong 391 clinical diagnosed cases within 48 hours after the onset of illness, 199 (treatment group) were given domestic oseltamivir phosphate and 192 (control group) were given compound pseudoephedrine hydrochloride sustained release capsules. In the next 10 days, symptoms, body temperature, adverse reaction of drugs, secondary diseases and combined drug use (including antimicrobial agents) were recorded .ResultsTwenty (10.05%) and 33 cases (17.19%) in treatment and control group needed to stay for observation, 5(2.51%) and 13 cases (6.77%) needed to be hospitalized in treatment and control group respectively, there were significant difference between two groups (0.01＜P＜0.05）; Average fever remission time were (40.15±21.86) h in treatment group and (65.92±29.08) h in control group respectively（P<0.0001）; Average flu symptoms remission time were (42.21±28.96) h in treatment group and (63.06±34.85) h in control group respectively（P<0.0001）; Average duration of flu symptoms in treatment group were 21 h shorter than control group. 92 of 481 (19.13%) close contacts in treatment group and 157 of 415 (37.83%) close contacts in control group developed influenza A (H1N1) (P<0.001), there was significant difference between the treatment and control group（ P＜0.001）. In observation period, the incidence of adverse drug reaction was 5.52% and 4.92% in treatment and control group respectively, there was no significant difference（P＞0.05）.ConclusionDuring pandemic influenza A (H1N1) outbreak, early use of domestic oseltamivir phosphate for treatment can relieve clinical symptoms effectively, reduce the hospitalization and observation rate, shorten treatment course, and reduce the incidence of the second generation influenza A (H1N1) in close contacts. Domestic oseltamivir phosphate has low incidence of adverse reactions, clinical application is safe and effective.