Objective To evaluate the clinical value of routine blood test parameters and four coagulation indices in the early severity assessment of atherosclerotic cerebral infarction (ASCI). Methods A retrospective study was conducted on 108 patients with atherosclerotic cerebral infarction admitted to Sanmenxia Third People’s Hospital from January 2022 to December 2025. According to the National Institutes of Health stroke scale (NIHSS) score on admission, the patients were classified into a mild group (n＝41), a moderate group (n＝39), and a severe group (n＝28). Differences in routine blood test and coagulation parameters among the three groups were compared. Correlation analysis was performed to determine the associations between relevant indicators and NIHSS score. Multivariate Logistic regression and receiver operator characteristic (ROC) curve analyses were used to assess the predictive value of these indicators for moderate-to-severe disease. Results Significant differences were observed among the three groups in white blood cell count (WBC), neutrophil count (NEU), lymphocyte count (LYM), neutrophil-to-lymphocyte ratio (NLR), prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen (FIB) level (all P＜0.05). With increasing disease severity, WBC, NEU, NLR, and FIB level increased progressively, whereas LYM, PT, and APTT decreased progressively. NIHSS score was positively correlated with WBC, NEU, NLR, and FIB level (all P＜0.05), but negatively correlated with LYM, PT, and APTT (all P＜0.05). Multivariate Logistic regression analysis identified elevated NLR and FIB as independent risk factors for moderate-to-severe disease in the early stage (all P＜0.05), whereas higher LYM was a protective factor (P＜0.05). ROC curve analysis showed that both NLR and FIB had good predictive value for moderate-to-severe disease, and their combined use achieved the best predictive performance. Conclusion Enhanced inflammatory response and hypercoagulability are present in the early stage of ASCI. NLR, LYM, and FIB are closely associated with disease severity, among which the combination of NLR and FIB provides better value for early severity stratification.