Intravenous phenobarbital is frequently offered to patients with generalized convulsive status epilepticus (GCSE) in China, but its long-term benefits are unclear. We aimed to evaluate the long-term effects of intravenous phenobarbital on adult patients with GCSE.This randomized clinical trial with a 12-month follow-up was performed in Xuanwu Hospital, Capital Medical University (Beijing, China) between February 2011 and December 2021. After the failure of intravenous diazepam treatment, adult patients with GCSE were randomized to receive either intravenous phenobarbital or valproate. Neurological outcome within 12-month was dichotomized as good (modified Rankin scale, mRS 0-2) or poor (mRS 3-6). Cognitive function was measured by mini-mental state examination (MMSE) and Montreal cognitive assessment (MoCA). Hamilton anxiety scale (HAMA) and Hamilton depression scale (HAMD) were tested for mood disorders.We consecutively recruited 166 patients with GCSE. After excluding individuals with termination after intravenous diazepam (n = 61), and with other exclusion criteria (n = 7), 98 patients were included and 88.0% (66/75) of survivors achieved seizure freedom at 12-month. Forty-five patients (45.92%) had good outcomes at 3-month and 57 patients (58.16%) had good outcomes at 12-month. And 46.67% (35/75) of survivors showed mRS improvement at 12-month (phenobarbital group, n = 17 vs. valproate group, n = 18, P = 0.321). Despite there was no significant difference with respect to good outcomes at 3-month (54.0% vs. 37.5%, P = 0.101), the rate of good outcomes in phenobarbital group was higher than valproate group at 12-month (68.0% vs. 47.92%, P = 0.044). A total of 43 patients successfully participated cognitive and emotional tests. Mild cognitive impairment was found in 7.14% of phenobarbital group and 50.0% in valproate group (P = 0.026). In addition, there were no significant differences with respect to anxiety (36.36% vs. 38.10%) and depression (31.82% vs. 47.62%) between the phenobarbital and valproate groups.Combined with long term conventional therapy, intravenous phenobarbital group had more good outcomes than intravenous valproate group in Chinese adult patients with GCSE up to 12-month follow-up. This finding may prompt the option of intravenous phenobarbital especially in patients with limited access to new antiseizure drugs.Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.