Objective To explore the renal artery diameter immediately after the renal sympathetic denervation (RDN) in patients with resistant hypertension. Methods Patients with resistant hypertension were enrolled in this study, and all patients were measured and recorded for the renal artery diameter values using the quantitative coronary angiography (QCA) before and immediately after the RDN. All the ablation parameters including starting impedance, terminal impedance, ablation power, and ablation point were recorded. Ambulatory blood pressure (BP) measurement was performed at the baseline and 6 months after RDN. Results A total of 12 patients with resistant hypertension were finally enrolled in this study. The mean ambulatory BP of the patients was (185±15)/(99±9) mmHg (1 mmHg=0.133 kPa) at admission, which was decreased by 31/15 mmHg in 6 months after RDN, showing significant difference compared with before RDN (P <0.001). The dilation of renal artery diameter was observed in all patients immediately after the RDN, with the mean renal artery diameter increased by 0.6 mm, also showing significant difference compared with before RDN (P <0.001). It was found that the renal artery diameter was correlated with the decrease of ablation impedance (the correlation coefficient = 0.74, P=0.006). However, the degree of renal artery diameter dilation could not predict the changes of BP after RDN (P >0.05). No peripheral vascular complications occurred in these patients. Conclusion RDN can significantly reduce the ambulatory BP in patients with resistant hypertension, and expand the renal artery diameter immediately. The degree of renal artery diameter dilation is positively correlated with the ablation impedance decrease, but it can not predict the long-term BP in patients.