Abstract: Objective To understand the etiology, clinical prognosis and risk factors of adult community-acquired acute bacterial meningitis （ABM） and provide the evidence for clinical diagnosis and treatment. Methods We performed a retrospective study of 181 clinically diagnosed hospitalized patients with community-acquired adult ABM from Jan.2010 to Jan.2018. The patients were categorized as non-elderly (16≤age＜65 years old, n=156 ) and elderly (age≥65 years old, n=25) group. The etiology, clinical features, prognosis and risk factors of the two groups were compared. Results Sixty-four of 181 patients (35.4%) had pathogens detected. The most common pathogens were Streptococcus pneumoniae (17.9%), Listeria monocytogenes (13.4%) and Klebsiella pneumoniae (10.5%). The mortality of the elderly group was higher than that of the non-elderly group (PStreptococcus pneumoniae, Listeria monocytogenes and Klebsiella pneumoniae.Pulmonary infection and temperature ≥38.5 ℃ are independent risk factors of poor prognosis in the non-elderly patients, as CSF pressure ≥200 mmH2O a independent risk factor in the elderly patients.