Objective To study the clinical features and prognostic factors of children with acute idiopathic myelitis.Methods This study retrospectively collected and summarized 75 patients' clinical data who were diagnosed with acute idiopathic myelitis for the first time in Children's Hospital of Chongqing Medical University from Jan.2003 to Dec.2012.The relationship between clinical features and prognosis was analyzed by using SPSS 19.0 software.Results In this study,37 boys and 38 girls were inclued.The distribution of ages was bimodal.The incidence of the disease seemed to have two peaks.One was broader ranging between age 1 and age 4 and the second was between age 9 and age 13.The main symptoms of acute idiopathic myelitis were weakness,sensory loss and autonomic dysfunction.Among the 75 cases,all patients had different degrees of paralysis,59.0％ (44 cases) of which had sensory abnormity and 80.0％ (60 cases) had autonomic dysfunction.In addition,root pain (50.7 ％,38/75 cases),bulbar paralysis (9.3 ％,7/75 cases) and fever(66.7％,50/75 cases) also appeared in the process.Seventy cases had spinal magnetic resonance imaging(MRI) exams,in which 61 showed abnormal signal and T2-weighted hyperintensities could be found.Forty children were followed up successfully and 32 of which had a good outcome.Factors associated with poor outcome included spinal shock(P =0.001),the duration of spinal shock beyond 2 weeks (P =0.015),low score of maximal neurologic defect (9.25 ± 0.89 vs 14.03 ± 2.87,P =0.000),plateau period ≥ 12 days (P =0.004),the time to maximal defect ≤ 24 hours(P=0.029),fever in initial stage(P =0.029),and being female(P =0.021).Conclusions Acute idiopathic myelitis was mainly manifested by weakness.Autonomic dysfunction happened more commonly than sensory abnormity.Some patients suffered bulbar paralysis during the couse of the disease.Spinal MRI signal usually changed on T2-weight sequences.Meanwhile,identifying the factors associated with poor outcome as early as possible is beneficial to preliminary evaluation and active treatment.