Background and objective: Adult demyelinating optic neuritis (ON) with positive myelin-oligodendrocyte glycoprotein antibody (MOG-Ab) has distinct clinical features. This study aimed to investigate the point prevalence, relationship with steroid dependency and prognosis value of MOG-Ab in adult ON. Methods: Clinical data analysis was undertaken in adults with ON admitted between December 2014 and January 2016. Patients were classified into three groups based on aquaporin-4 antibody (AQP4-Ab) and MOG-Ab status: AQP4-ON, MOG-ON and seronegative-ON. Results: A total of 158 adults with ON (190 eyes) were assessed, including 31 MOG-ON (19.6%), 67 AQP4-ON (42.4%) and 60 seronegative-ON (38.0%) cases. The female-to-male ratio was significantly lower in MOG-ON (1.8:1) than that in AQP4-ON (8.6:1) groups (p = .005). The median age, percentage of bilateral ON and visual loss at the nadir at onset was similar among the three groups. Thirty-eight eyes (76%) in the MOG-ON group showed good visual recovery (> 20/40) in the final visit, which is statistically better than that in the AQP4-ON and seronegative-ON groups (p < .001 and p = .006, resoectively). Fifteen adults with ON (9.5%) showed dependency on steroid, which was particularly prominent in the MOG-ON group (11/31, 35.5%) and rarely presented in the AQP4-ON (2, 3.0%) and seronegative-ON (2, 3.3%) groups. Results suggested less loss of pRNFL in MOG-ON than that in AQP4-ON group (p < .001), and a larger proportion of canalicular segment involved in MOG-ON adults (p = .007 and p < .001). Conclusion: MOG-ON had the smallest proportion of acute demyelinating ON in Chinese adults. One third of adults with MOG-ON predominantly showed a substantial dependency on steroids and relapse on steroid reduction or cessation, which rarely presented in AQP4-ON and seronegative-ON adults.