Abstract： Objective To observe the effects of seawater immersion on the healing process of open tibial fracture in rabbits.Methods Forty-four New Zealand rabbits were randomly divided into two groups: the experimental group (group A) and the control group (group B), each consisting of 22 animals. The 2 groups of animals all had bilateral open fracture of tibia. The wounded limbs of the animals in group A were immersed in the artificial seawater for 3 hours. And the animals in group B were left there untended for 3 hours. Following debridement, wounds were sutured. Lesion of osteoblast, vascular endothelial growth factor (VEGF),the expression of transforming growth factor-β1 (TGF-β1) and the process of porosis in the animals of both groups were observed on the 7th,14th,21st and 28th days respectively under the electron and optical microscopes.Results (1) Under the electron microscope, obvious lesion of osteoblast in the animals of group A was observed at the fractured sites, 7-14 days after the fracture, displaying cell membrane and nuclear membrane damage, mitochondrial swelling and vacuolation, cell nucleus dissolution and necrosis. On the 21st and 28th days, morphology of osteoblasts in the animals of group A returned to normal. (2) Immunohistochemistry indicated that the expression of VEGF and TGF-β1 in the animals of group A increased and gradually rose to the peak on the 14th day after fracture, and then decreased. The expression of VEGF and TGF-β1 was not delayed in the animals of group A, but their expression intensity at various times was all obviously weaker than that of group B.(3)On the 28th day, for the animal in group B, 15 limbs were of complete osseous callus, accounting for 75%, while 5 limbs were of mixed type osseous callus, accounting for 25%. For the animal in group A, 6 limbs were of complete osseous callus, accounting for 30%, while 14 limbs were of mixed type osseous callus, accounting for 70%. Significant statistical differences could be seen, when a comparison was made between the groups(P<0.01).Conclusions The process of intramembranous/cartilaginous ossification and fracture healing delayed, following open fracture of limbs coupled with 3-hour seawater immersion.