Ｏｂｊｅｃｔｉｖｅ　To evaluate whether the changes in the radial artery pulse pressure (rPP) can predict the changes in stroke volume (SV) after fluid challenge in patients after cardiac surgery.　Methods　This prospective observational study included 75 mechanical ventilated patients with hypotension after cardiac surgery, where all the patients involved underwent rPP and SV measurement after fluid challenges. Accordingly, the patients were divided into a volume responder group (increases in SV≥15%, n=45) and a non-responder group (increases in SV<15%, n=30). Then, heart rate (HR), blood pressure(BP), mean arterial pressure (MAP), central venous pressure (CVP), SV and stroke volume variation (SVV) were collected at baseline level and after fluid challenges respectively. The ability of the indices to predict fluid responsiveness, the area under the receiver operating characteristic curve (AUC), sensitivity and specificity for predicting fluid responsiveness were calculated. 　Results　In the study, 60% of the patients were defined as fluid responders. BP, MAP, CVP, SV increased significantly in the volume responder group(P<0.05), while HR and SVV tended to decrease. Increases in rPP induced by fluid challenges (≥13%) indicated SV increases (≥15%) with a sensitivity of 0.82 and a specificity of 0.83. The AUC was 0.90 [95% confidence interval(CI) 0.81-0.96]. 　Conclusions　The changes in rPP induced by fluid challenges can be used to predict the changes in SV in patients after cardiac surgery.