Objective To explore the correlations between serum soluble growth stimulation gene 2 protein (sST2), brain natriuretic peptide (BNP) and the degree of carotid atherosclerosis in patients with acute ischemic stroke. Methods A total of 205 patients with acute ischemic stroke were selected as study group, and were divided into mild group with 100 cases, moderate group with 70 cases, and severe group with 35 cases according to the severity of carotid atherosclerosis. Another 150 healthy people who received physical examination during the same period were selected as control group. Serum levels of sST2 and BNP were compared among all groups. The correlations of sST2 and BNP levels with the degree of carotid atherosclerosis were analyzed. The influencing factors of different degree of carotid atherosclerosis in patients with acute ischemic stroke were analyzed. The predictive value of sST2 combined with BNP on the degree of carotid atherosclerosis in patients with acute ischemic stroke was analyzed. Results The serum sST2 level of the study group was significantly lower than that of the control group, and the serum BNP level was significantly higher than that of the control group (P < 0.05). The sST2 levels in moderate and severe groups were significantly lower, BNP levels were significantly higher than that in the mild group (P < 0.05). BNP level in the severe group was significantly higher, sST2 level was significantly lower than that in the moderate group (P < 0.05). The degree of carotid atherosclerosis in patients with acute ischemic stroke was correlated with age, history of hypertension, history of smoking, history of diabetes, levels of total cholesterol (TC), C-reactive protein (CRP), homocysteine (Hcy) and low density lipoprotein (LDL) (P < 0.05). Age, hypertension history, smoking history, diabetes history, TC, CRP, Hcy, LDL, BNP and sST2 were the influencing factors for degree of carotid atherosclerosis (P < 0.05). Serum BNP level was positively correlated with the degree of carotid atherosclerosis, while sST2 level was negatively correlated with the degree of carotid atherosclerosis (P < 0.001). The area under the curve (AUC) for the combined prediction of sST2 and BNP was significantly greater than that for the individual prediction of sST2 and BNP (P < 0.001). Conclusion Clinical observation of the changes in serum levels of sST2 and BNP in patients with acute ischemic stroke can effectively assess the progression of the disease, which is beneficial for improving the severity of carotid atherosclerosis in patients. The combined assessment of sST2 and BNP shows good diagnostic performance for evaluating the severity of carotid atherosclerosis in patients with acute ischemic stroke.