The Circle of Willis perforation (cWp) mouse model is a key tool in subarachnoid hemorrhage (SAH) research; however, inconsistent bleeding volumes can challenge experimental reliability. To address this issue, we introduced the ROB Scoring System, a novel protocol integrating Rotarod Tests (RT), Open-field Tests (OT) video analysis, and daily Body Weight Loss (BWL) monitoring to precisely categorize SAH severity. Forty C57BL/6 mice underwent cWp induction, categorized by ROB into severity subgroups (severe, moderate, mild). Validation compared ROB outcomes with autopsy results on postoperative days 3 and 7 for acute and sub-acute evaluations. Mortality rates were analyzed via the survival log-rank test, revealing a significant difference among severity groups (P < 0.0001). Strong correlations between ROB grades and autopsy findings underscored its precision. Notably, the severe group exhibited 100% mortality within 4 days post-SAH onset. Individual parameters (RT, OT, BWL) were insufficient for distinguishing SAH severity levels. The ROB Scoring System represents a significant advancement, offering precise categorization and addressing inherent bleeding variations in the cWp mouse model. This standardized protocol enhances the reliability and effectiveness of SAH research, providing a valuable tool for future investigations into this critical.