Objective To investigate the effect of seawater immersion on periosteal function of the soft tissue with open injury in rabbit limbs.Methods Forty-eight New Zealand rabbits were used in the experiment.The animal model of open soft tissue injury was developed by cutting open the hindlimbs,and then the animals were randomly divided into 3 groups:the simple injury group or the control group ( group A),the injury plus 30 min seawater immersion group (group B),and the injury plus 1 h seawater immersion group (group C).Rabbits were sacrificed following surgery on 0,1,3,7 days,and histopathology and expressions of TNF-α and TGF-β1 were observed and monitored from the collected periosteum.Results (1) Inflammatory response of periosteum resulting from limb surgery plus 30 min seawater immersion was more serious than that of the animals in the control group.The longer the immersion,the more serious the response.(2) Intramembranous bone formation delayed markedly,following 1 h seawater immersion,however,for the animals in group B,delay in intramembranous bone formation was insignificant. (3) Periosteal malpighian layer cells for the animals in group B increased significantly,following injury on 1,3,7 days.Marked differences could be seen,when comparisons were made with animals of group A and group C (P ＜ 0.01 ).Though periosteal malpighian layer cells for the animals in group A increased,when compared with those of the animals in group C,no significant differences could be noted between them ( P ＞ 0.05 ).(4) Expressions of TNF-α were all seen in periosteal osteoprogenitor cells and osteoblasts in the animals of the 3 groups.The expression reached peak on day 1 after surgery,then,decreased gradually,with the expression level increased with the extension of seawater immersion. (5)There were expressions of TGF-β1 in periosteal osteoprogenitor cells and osteoblasts in the animals of the 3 groups and persistent expression of TGF-β1 could be observed on day 0 to day 7,and the expression of TGF-β1 in the animals of group B was obviously stronger than those of the animals in group C and group A.Conclusions Seawater immersion could aggravate periosteal damage,and 1 h seawater immersion could obviously delay and damage the capability of intramembranous bone formation of periosteum, indicating that the longest endurance of periosteum with seawater immersion could be less than 1 hour.