Objective To investigate the correlation between plasma aminoterminal pro-B-type natriuretic peptide (NT-proBNP) level and severity of coronary artery lesions in patients with non-ST segment elevation myocardial infarction (NSTEMI). Methods NSTEMI patients presenting to the Emergency Department and Department of Cardiology from January 2013 to March 2017 were divided into four groups: thrombosis without stenosis, single vessel disease, double vessel diseases, and three vessel diseases. The general situation of the patients, the plasma NT-proBNP, troponin T, echocardiogram and coronary angiography results were analyzed. Results A total of 88 patients were included including 6 in thrombosis without stenosis group, 20 in single vessel disease group, 31 in double vessel diseases group, and 31 in three vessel diseases group. The NT-proBNP level, left ventricular ejection fraction, left ventricular end diastolic diameter, and coronary Gensini score in three vessel diseases group differed much from those in the other groups (P<0.05). The correlation of NT-proBNP with coronary Gensini score in all the patients was positve (t=0.663, P<0.05). Conclusion The level of plasma NT-proBNP in patients with NSTEMI is related to the severity of coronary artery disease.