Objective：To investigate the perioperative effect of aortic root enlargement for adult patients with small aortic root undergoing aortic valve replacement. Methods：Twenty cases with small aortic root underwent aortic root enlargement and aortic valve replacement as the research group from 2018 to 2019，150 cases with normal aortic root underwent aortic valve replacement as the normal aortic root group，and 143 patients with small aortic root underwent aortic replacement rather than root enlargement as the small aortic root group from 2013 to 2018. The inverse probability of treatment weighting（IPTW）method was used to balance the difference of baseline parameters among the three groups，and logistic multivariate regression was used to detect the independent risk factors of postoperative increase in aortic valve pressure gradient. Results：After the IPTW，one month after aortic valve replacement，the peak aortic valve pressure gradients of the normal aortic root group，the small aortic root group，and the research group were（26.79 ± 10.85）mmHg，（36.88 ± 19.27）mmHg，and（20.85 ± 6.25）mmHg. The differences of the pairwise comparison were still statistically significant（P < 0.01）. Multivariate logistic regression analysis showed the treatment strategy of aortic root［small aortic root without aortic root enlargement，β（95%CI）：8.48（2.17~14.80），P=0.010；small aortic root underwent aortic root enlargement，β（95%CI）：-12.16（-21.79~2.52），P=0.015］and preoperative peak aortic valve pressure gradient［β（95%CI）：0.17（0.03~0.30），P=0.020］were independent risk factors for increased peak aortic valve pressure gradient. Conclusion：For patients with small aortic root，the short-term hemodynamic effect after aortic root enlargement is better，but the long-term clinical results need further follow-up.