BACKGROUND: Since the 1990s, liver grafts from non-heart-beating donor (NHBD) have become an alternative because of the deficiency of grafts from heart-beating-do-nors (HBDs). Warm ischemia injury, however, directly influences the grafts'activity and functional recovery after operation. We investigated the microcirculatory change of liver graft at different warm ischemia time (WTT) in rats and determined the maximum limitation of liver graft to warm ischemia. METHODS: According to WIT, 120 rats divided ran-domly into 5 groups of 0, 15, 30, 45, 60, minutes respec-tively. The microcirculatory changes of their liver grafts were measured including serum level of hyaluronic acid (HA) and ultrastructural changes. After orthotopic liver transplantation (OLT), the recovery of microcirculation of the liver grafts after 24 hours, 48 hours and 3 days was ob-served. RESULTS: Microcirculatory changes and function of the liver grafts became normal after reperfusion when the WTT was less than 30 minutes. In the 45-minute WI group, part of blood sinusoids was full of cytoplasmic blebs stemming from the microvili of hepatocytes and hemocytes. The se-rum level of HA in each group after 45 minutes of WI re-covered after reperfusion. CONCLUSIONS: The microcirculatory change of rat liver graft is reversible when the WIT is less than 30 minutes: rat liver graft could be safely subject to warm ischemisa within 30 minutes. The maximal 45 minutes of WI can be tolera-ted by the microcirculatory function of liver graft. After 60 minutes of WI, irreversible disturbance of microcirculation may appear.