Abstract: Objective　To explore the effect of compound-24 (C-24), a non-peptide orphanin receptor (ORL1) antagonist, on arrhythmia after acute myocardial ischemia in rats. Methods　A total of 50 clean-grade healthy male SD rats were divided into 5 groups according to the random number table method, including sham operation group (Sham group), coronary artery ligation group (CAO group) and C-24 group (C group). The C group was divided into three subgroups, namely C-I group (1×10-13 mol/L), C-Ⅱ group (1×10-11 mol/L) and C-Ⅲ group (1×10-9 mol/L). The left anterior descending coronary artery was ligated to prepare the rat model of acute myocardial ischemia in the CAO group and C-24 group. The three subgroups of C-24 were injected with the corresponding concentrations of C-24 via the tail vein at 10 min before ligation. The heart rate variability (HRV) indicators, cardiac function data and score arrhythmia within 15 minutes after ligation were recorded in each group of rats. After 15 minutes of coronary artery ligation, the rats were sacrificed and myocardial tissues were collected. Enzyme-linked immunosorbent assay (ELISA) was used to detect the concentrations of the rat myocardial inflammatory factors, tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β). The correlation between the number of ventricular premature beats and TNF-α and IL-1β was analyzed. Results　Compared with the Sham group, the number of VEBs increased significantly within 15 minutes after coronary artery occlusion, the number of occurrence of ventricular tachycardia (VT) + ventricular fibrillation (VF) increased and the duration was prolonged, and the arrhythmia score increased in the CAO group (P＜0.05). The standard deviation of the RR interval (SDNN) and the root mean square (RMSSD) of the adjacent RR interval difference in HRV indicators were significantly reduced (P＜0.05). The ratios of low and high frequency (LF/HE) increased (P＜0.05), and the levels of TNF-α and IL-1β in myocardial tissue were significantly increased. Compared with the CAO group, the numbers of VEB occurrences were significantly reduced in the C-Ⅰ group, C-Ⅱ group and C-Ⅲ group. The number and duration of VT+VF decreased, and the arrhythmia score and LF/HF decreased in the C-Ⅲ group (P＜0.05). Compared with the CAO group, the levels of TNF-α and IL-1β were significantly decreased in C-Ⅱ group and C-Ⅲ group (P＞0.05). Correlation analysis showed that the levels of TNF-α and IL-1β were positively correlated with the number of VEB occurrences (r=0.620, 0.609, P＜0.01). During the experiment, there were no significant differences in systolic blood pressure (LVSP), left ventricular end diastolic pressure (LVEDP), heart rate (HR) and the maximum change rate of left ventricular pressure (±dp/dtmax) in the five groups. Conclusion　C-24 can reduce the occurrence of arrhythmia and the production of inflammatory factors in myocardial tissue after acute myocardial ischemia, and has no significant effect on cardiac function.