Abstract: Objective To observe the impact of insulin resistance (IR) on infarct size and cardiac function of non-diabetic patients at early stage of acute NSTEMI. Methods Sixty-nine non-diabetic patients with NSTEMI in Chinese PLA General Hospital from January 6 to July 31 in 2014 were consecutively enrolled in the study. 18-lead ECG was acquired within 10 minutes after admission of each patient, and the sum of ST-segments depression (Sum STD) was calculated. On the 2nd day, the values of left ventricular ejection fraction (LVEF), left ventricular end diastolic volume (LVEDV) and left ventricular end systolic volume (LVESV) were assessed in all patients with echocardiogram. The homeostatic model assessment index (HOMA index) was also determined on the 2nd day after admission. The patients were divided into insulin resistance (IR) group (HOMA index≥1.7) and non insulin resistance (NIR) group (HOMA index< 1.7) according to their HOMA index. The tests of serum creatinine kinase (CK), creatinine kinase MB (CK-MB) and N-terminal pro brain natriuretic peptide (NT-pro BNP) were carried out every 6 hours in the first 48 hours after admission to determine the peak values of CK, CK-MB and NT-pro BNP. Results Of the 69 patients, 39 (57%) patients were included in IR group while the other 30 patients were included in NIR group. There was no significant difference in basic clinical characteristics including age, sex, histories of smoke, hypertension, hypercholesterolemia, the average time of symptom onset to admission and Killip class on admission (P> 0.05). Compared with NIR group, the Sum STD and the peak release of CK, CK-MB, NT-pro BNP in patients of IR group was significantly higher (P< 0.01). The average values of left ventricular end diastolic volume (LVEDV) were similar between two groups while the average value of left ventricular end systolic volume (LVESV) in IR group was significantly higher than in IR group (P< 0.01). The average value of left ventricular eject fraction (LVEF) in IR group was significantly decreased compared with NIR group (P< 0.01). Conclusion This research shows high incidence of acute IR at early stage of NSTEMI in non-diabetic patients. The non-diabetic patients with IR has larger infarct size and more seriously impaired leftventricular systolic function than patients without IR at early stage of acute NSTEMI.