Abstract: It is very important for pathologist to infer the injury time in body. in this paper, we observed the changes of histamine and 5-HT in Rat's skin blunt wound with biochemical methods. We found the histamine and 5-HT increased in the antemortem injury.The highest point of histamine showed in the 20 minute after injury,the highest point of 5-HT showed in the 5 minute, the second point of 5-HT showed in the 30 minute. in the other hand,we found no changes of histamine and 5-HT happened in the postmortem injury. We analysed the changing regulation of histamine and 5-HT in aid of forensic expertizing practice.