Introduction: Cerebral venous thrombosis (CVT) is a rare subtype of stroke. However, existing scales were insufficient to evaluate the overall severity of CVT. The aim of this study is to develop and validate a CVT severity scale.Methods: Items 1-11 were directly derived from NIHSS. New items were generated from a literature review and focus group discussion. A total of 170 CVT patients were prospectively recruited from 26 top tertiary hospitals in China Mainland from January 2021 to May 2022 to validate the CVT severity scale. The CVT severity scale, NIHSS, mRS and GCS were rated at admission. The lumbar puncture opening pressure was also recorded. Twenty randomly selected CVT patients were rated with the CVT severity scale again 24 hours later. The clinical outcome of CVT was evaluated by mRS at 6 months after baseline.Results: We successfully established a CVT severity scale with 18 items. Exploratory factor analysis showed that 18 items were attributed to factor 1 (focal neurological deficits), factor 2 (diffuse encephalopathy), factor 3 (intracranial hypertension) and factor 4 (cavernous sinus syndrome). CVT severity scale was positively correlated with ICP, NIHSS and mRS, and negatively correlated with GCS at baseline. CVT severity scale >3 or factor 3 >2 indicated intracranial hypertension. CVT severity scale >10 indicated poor clinical outcome at 6 months of follow-up. Meanwhile, CVT severity scale showed high internal consistency and test-retest reliability. Conclusion: The CVT severity scale included 18 items encompassing 4 domains of focal neurological deficits, diffuse encephalopathy, IH and cavernous sinus syndrome. CVT severity scale correlated well with ICP, NIHSS, mRS and GCS. Patients with CVT severity scale >10 can be defined as severe CVT. The CVT severity scale may serve as a valid and reliable tool for measuring the overall severity of CVT.