Abstract: Objective Epidemic of influenza A H7N9 occurs in mainland China during the annual winter and spring seasons. The increasing tendency of human infection and high mortality leads to a growing focus on the exploration of prognostic factors associating with risk of death in H7N9 human infection. Our research is to explore the prognostic factors associating with risk of death in H7N9 infection cases, to decrease the mortality of severe H7N9 patients and to increase their life qualities. Methods A total of 121 laboratory-confirmed patients were divided into survival and death groups. Clinical data of enrolled patients were compared between two groups. Logistics regressions were conducted to explore the association of death risk and potential prognostic factors. Results Lower level of GFR, PCT, low value of calcium and low value of blood pH were found in death group (all P<0.05). However, higher level of age, CRP, BNP, peak and low value of sodium, chlorine and low value of potassium were also found in death group (all P<0.05). Larger proportion of death cased were given intubation, ECMO and CRRT (all P<0.05). Logistics regression further validated low value of blood pH was associated with death risk (P<0.001). When 0.1 unit of the minimal value of blood pH decrease, the risk of death increased 0.304 folds. Conclusion Decline of blood pH is an independent risk factor associating with death in H7N9 infection, indicating that monitoring blood pH and keeping acid-base balance in H7N9 infected patients maybe a key therapeutic strategy in clinic.