Objective To assess the relationship between early mortality and degree of prosthesis-patient mismatch(PPM) after aortic valve replacement surgery using risk-adjusted mortality of EuroSCORE Ⅱ . Methods The clinical data of 1 247 consecutive patients who underwent aortic valve replacement from Jan. 1, 2007 to Dec. 31, 2011 in our hospital were retrospectively analyzed. The EuroSCORE Ⅱ-predicted mortality and the effective orifice area index (EOAi) of artificial aortic valve were calculated for each patient. The patients were divided into three groups according to aortic EOAi: non-to-mild PPM, moderate PPM, and severe PPM. Risk-adjusted mortality and 95% confidence interval were calculated for each group. The EuroSCORE Ⅱ-predicted mortality and risk-adjusted mortality were compared among three groups. Results The observed mortality was 2.79% (29/1 040) for patients with non-to-mild PPM, 5.00% (8/160) for patients with moderate PPM, and 8.51% (4/47) for patients with severe PPM, with significant differences found between groups (P<0.05) . There were no significant differences in EuroSCORE Ⅱ-predicted mortalities among the three groups (2.82% for the non-to-mild PPM group, 2.69% for the moderate PPM group, and 2.72% for the severe PPM group). And the risk-adjusted mortality of non-to-mild PPM group (0.99, 95%CI: 0.93-1.05) was significantly lower than those of moderate PPM group (1.86, 95%CI: 1.68-2.08) and severe PPM group (3.13, 95%CI: 2.56-4.00). Conclusion High degree of aortic PPM after aortic valve replacement is associated with increased operative mortality.