Abstract: AIM To investigate the effect of 4,4’-Diisothiocyanostilbene-2,2’-disulfonic acid(DIDS) on the hemodynamic parameters, arrhythmia and creatine kinase(CK)/lacate dehydrogenase(LDH) of myocardium in the rat model of ischemia/reperfusion injure(I/RI) in vivo. METHODS SD rats (male) were divided into five groups; sham-operation group, I/R group, I/R+ DIDS (7 mg/kg) group, I/R+ DIDS (14 mg/kg) group and I/R+ DIDS (28 mg/kg) group, with 5 rats in each group. In DIDS group, the rats were administered by program controlled micro pump injection of DIDS 2 h ［4 ml/(kg·h)］ at the beginning of reperfusion. The hemodynamic parameters were determined by multiple channel electrophysiolograph before and after ischemia, and after reperfusion. The ECG changes were recorded incessantly from myocardial ischemia to reperfusion and the results were analyzed and given score. The activities of plasma CK and LDH were measured after reperfusion. RESULTS ①DIDS improved haemodynamics indexes. Compared with those in sham-operated group, left ventricular end diastolic pressure (LVEDP) significantly increased while left ventricular systolic pressure (LVSP), maximal rate of increase of ventricular pressure (dp/dtmax) and maximal rate of decrease of ventricular pressure (dp/dtmin) decreased markedly in I/R group (P<0.05). ②DIDS lowered the arrhythmia score. After 30-minute ischemia and 4-hour reperfusion, the arrhythmia score in sham-operation group, I/R group, DIDS (7 mg/kg) group, DIDS (14 mg/kg) group and DIDS (28 mg/kg) group were respectively 1.20 ±0.45, 4.57±1.62, 3.97±1.51, 3.23±1.13 and 3.56±1.47. DIDS markedly lowered the arrhythmia in reperfusion phase (P<0.05), especilly in 14 mg/kg group (P<0.01). ③DIDS significantly reduced the activities of plasma CK and LDH (P<0.05). CONCLUSION DIDS protects the heart by lowering arrhythmia in reperfusion phase, inhibiting release of LDH and CK and improving heart function during I/RI.