Objective The purpose of this study was to screen prognostic factors in elderly patients with severe craniocerebral injury from PNI, NIHSS scores and other clinical factors, and to evaluate the prognosis of elderly patients by stratification. Methods This study retrospectively analyzed the clinical data of elderly patients with severe craniocerebral injury who were admitted to the neurosurgery department of Hai'an People's Hospital from March 2019 to March 2024. Multivariate COX regression analysis was used to screen independent prognostic risk factors. Results Multivariate COX analysis showed that NIHSS was an independent risk factor for poor prognosis in elderly patients with severe craniocerebral injury (HR>1, P<0.05). PNI was an independent protective factor for good prognosis in elderly patients with severe craniocerebral injury (HR<1, P<0.05). Patients with high NHISS score had a worse prognosis than those with low NHISS (P<0.05). Patients with high PNI had a better prognosis than those with low PNI (P<0.05). Patients with low NHISS score and high PNI had the best prognosis, while patients with high NHISS score and low PNI had the worst prognosis. Conclusion NIHSS score and PNI are independent risk factors for poor prognosis and independent protective factors for good prognosis in elderly patients with severe craniocerebral injury. The NHISS score and PNI can be used in combination to guide prognostic risk stratification in older patients with severe craniocerebral injury, help identify patients with poor prognosis, and provide personalized treatment at an early stage of injury.