Objective To assess the efficiency and safety of mycophenolate mofetil (MMF) in patients with multiple sclerosis (MS) and neuromyelitis optica (NMO). Methods Twenty-seven patients with MS or NMO were selected, and the patients were divided into 2 groups:MMF group (MMF combined with glucocorticoid treatment group, 10 cases) and glucocorticoid group (only glucocorticoid treatment group, 17 cases). There were 5 cases with MS and 5 cases with NMO in MMF group. There were 13 cases with MS and 4 cases with NMO in glucocorticoid group. The therapeutic efficacy 6 months after treatment, expanded disability status scale (EDSS) before treatment and 6 months after treatment, and annualized relapse rate (ARR) were compared; and the safety was observed. Results There was no statistical difference in efficacy rate 6 months after treatment between MMF group and glucocorticoid group: 9/10 vs. 11/17, P>0.05. The EDSS scores 6 months after treatment in MMF group and glucocorticoid group were significantly lower than those before treatment: (2.41 ± 2.05) scores vs. (3.40 ± 2.05) scores and (1.17 ± 0.92) scores vs. (2.38 ± 1.28) scores, and there were statistical differences (P<0.05), particularly for the patients with MS. The ARR 6 months after treatment in MMF group was significantly lower than that before treatment: 0 time/year vs. 0.75 times/year, and there was statistical difference (P<0.05). The difference of ARR before and after treatment in MMF group was significantly higher than that in glucocorticoid group: 0.75 times/year vs.- 0.46 times/year, and there was statistical difference (P<0.01), particularly for the patients with MS. Only 1 female patient had myalgia when taking higher dosage of MMF, and the symptom tended to relieve after the dosage was reduced. Conclusions MMF is effective in the treatment of MS and NMO. MS can improve the neurological function and reduce the recurrence of the disease;and the safety is high.