Thirty-six male Sprague-Dawley rats were used and divided into 3 groups(N=12):simple hemorrhagic shock group,salinetreated group,and naloxone-treated group.A new method by synchronous video tape recording with 2cameras simple was established to observe the relationship between the changeof blood pressure and that of microcirculation of cremaster muscle.It wasshown that the plugging of WBC in capillaries might be the reason for noreflow in microvessels after transfusion and infusion during irreversibleshock state.Administration of naloxone followed by reinfusion of the shedblood increased blood pressure and pulse pressure.With the increase of pulsepressure a pulsed blood flow rushed the stationary of blood cells in capil-laries,which eventually pushed them away and led to reperfusion in capillaries.This made blood pressure and velocity of blood flow increase withsteadiness.The 24-hour survival rate was significantly increased in naloxone-treated group(10/12),as compared with that in saline-treated group(1/12).The mechanism of naloxone treatment was discussed.It was suggested thatthe effects of cardiac and microcirculatory event may influence each other,which plays an important role in the pathogenesis of irreversible hemorrhagicshock. Thirty-six male Sprague-Dawley rats were used and divided into 3 groups (N = 12): simple hemorrhagic shock group, salinetreated group, and naloxone-treated group. A new method by synchronous video tape recording with 2 cameras simply was established to observe the relationship between the changeof blood pressure and that of microcirculation of cremaster muscle. It wasshown that the plugging of WBC in capillaries might be the reason for noreflow in microvessels after transfusion and infusion during irreversible shock state. Administration of naloxone followed by reinfusion of the shedblood increased blood pressure and pulse pressure. The increase of pulsepressure a pulsed blood flow rushed the stationary of blood cells in capil-laries, which eventually pushed them away and led to reperfusion in capillaries. This made blood pressure and velocity of blood flow increase with stability. The 24-hour survival rate was significantly increased in naloxone-treated group (10/12), as compared with that in sal ine-treated group (1/12). The mechanism of naloxone treatment was discussed. It was suggested that the effects of cardiac and microcirculatory events may influence each other, which plays an important role in the pathogenesis of irreversible hemorrhagicshock.