Objective To explore the relationship between Platelet-to-neutrophil ratio and neurological impairment and prognosis in patients with acute cerebral infarction. Methods A total of 145 ACI patients from January 2018 to December 2018 in the Department of Neurology of Jiangsu People"s Hospital were selected. The patients were divided into 112 patients with good prognosis (mRS score 0-2) and 33 patients with poor prognosis (mRS score 3-6) according to the prognosis score of 90 days after discharge. Baseline data were collected and blood test related indicators were determined. Result Compared with ACI patients with good prognosis, there were significant differences in gender, age, coronary heart disease, NIHSS score, white blood cell count, lymphocyte count, neutrophil count, PLR and P NR in poor prognosis group (P<0.05). Logistic regression analysis showed that age (OR=1.053, P=0.047), NIHSS (OR=1.395, P=0.000), PLR (OR=1.015, P=0.010) were risk factors for poor prognosis of ACI patients, and PNR (OR=0.970, P=0.036) were protective factors. Spearman correlation analysis showed that PNR was negatively correlated with mRS, NIHSS and Essen scores in ACI patients (r=-0.212, P=0.010, r=-0.173, P=0.039, r=-0.271, P=0.001). ROC curve analysis showed that AUC of PNR level was 0.666, and the best diagnostic value of PNR was 51.496, P<0.05. Conclusion PNR is associated with neurological impairment in ACI patients and is a protective factor for prognosis of cerebral infarction. PNR can predict the prognosis of ACI.