Objective To explore the predictive value of mucosal vascular pattern (MVP) for inflammation and angiogenesis in ulcerative colitis (UC) under narrow-band imaging (NBI) colonoscopy. Methods Forty-two patients with UC were recruited for NBI colonoscopy between 2012 and 2015 at Peking Union Medical College Hospital. For each segment with lesion, the NBI image was saved and at least one biopsy specimen was obtained for histological assessment. MVP of each image was determined by two trained endoscopists with consensus. The degree of inflammation was graded by using a histological colitis score from zero to four. The immunohistochemical staining of endothelin marker CD31 was performed and microvascular density was assessed by vessel count. Semi-quantitative vascular endothelial growth factor (VEGF) expression was evaluated immunohistochemically. The histological variables were assessed by a pathologist who was blinded to the endoscopic findings. Results MVP in 119 colorectal segments from 42 patients was assessed under NBI colonoscopy. The results showed 34 segments of clear MVP, 58 of obscure MVP and 27 MVP absence. The classification of MVP was correlated with the degree of inflammation (r=0.824, P <0.001). There was a trend towards a growing level of microvascular density (P <0.001) and VEGF expression (P <0.001), with the varying classifications of MVP. A significantly positive relationship (r=0.961, P<0.001) between microvascular density and VEGF expression was observed. Conclusion The classification of MVP under NBI colonoscopy may be a useful tool for prediction of the grade of mucosal inflammation and angiogenesis in UC.