AIM: To investigate the related-factors analysis of extra-ocular muscle paralysis in pediatric ocular myasthenia gravis(OMG). METHODS: A retrospective, observational cohort study was performed of 203 pediatric patients diagnosed with OMG between Nov.2011 and May 2020 at Wuhan Children's Hospital. Data on clinical features and laboratory indicators of children with OMG were statistically analyzed between extra-ocular muscle paralysis group and non-extra-ocular muscle paralysis group, which were classified by pediatric ophthalmologists based on ocular manifestations. The Logistic regression analysis was performed immediately after that to determine the independent factors. RESULTS: Totally 203 pediatric OMG, 97(47.8%)had extra-ocular muscle paralysis with various clinical features including strabismus(n=69, 71.1%), torticollis(n=18, 18.6%). Among the 97 children, 79(81.4%)patients were presented with monocular involvement, of which 53(54.6%)had single extra-ocular muscle paralysis. The most common was medial rectus muscle(n=19, 35.8%). Between extra-ocular muscle paralysis group and non-extra-ocular muscle paralysis group, there were statistically significant difference(P<0.05)in age, serum immunoglobulin M(IgM), serum free triiodothyronine(FT3), serum thyroglobulin, and glucocorticoid combination pyridostigmine bromide therapy(72.2% vs 38.7%). Furthermore, the level of FT3(OR=2.006, 95%CI: 1.233-3.263)and glucocorticoid combined treatment(OR=4.328, 95%CI: 1.936-9.677)were the related-factors affecting the extra-ocular muscle paralysis of children with ocular myasthenia gravis. CONCLUSION: Extra-ocular muscle paralysis was the common ocular manifestation in pediatric OMG. Monocular involvement was more common than binocular involvement especially the medial rectus muscle, while diplopia was rare. The level of FT3 can be considered as an important immune indicator to evaluate extra-ocular muscle paralysis in children with ocular myasthenia gravis.