Abstract: ob＜x＞jective To compare the effectiveness and safty of short axis - out of plane ultrasound guided method and direct palpation method in the radial artery catheterization of patients with atrial fibrillation. Methods Seventy patients with atrial fibrillation who underwent cardiac surgery in The First Affiliated Hospital of Nanjing Medical University from December 2019 to June 2020 were divided into two groups by random number table method: short axis-out of plane ultrasound guided group (UG group) and direct palpation group (TP group).The first puncture success rate, first catheterization success rate, completion rate within 3 minutes, overall success rate, the times of catheterization attempts, numbers of puncture site, catheterization time , the rate of damage to the posterior wall of the radial artery and the incidence of subcutaneous hematoma during the puncture, and the incidence of subcutaneous ecchymosis on the first day after the operation were observed. Results Compared with the TP group, the first puncture success rate, the first catheterization success rate, the completion rate within 3min and the overall success rate of UG group were significantly increased （P <0.05）, the times of catheterization attempts, numbers of puncture site, catheterization time were decreased（P <0.05）, the rate of posterior wall damage ，subcutaneous hematoma and subcutaneous ecchymosis were also significantly decreased（P <0.05）. Conclusion Short axis - out of plane ultrasound guided radial artery catheterization is safe and effective choice for patients with atrial fibrillation with high success rate, short operation time and few complications