Abstract: The experiment gave a research on decomposition kinetics of phenobarbital in preserving blood of rabbit (in room 10 to 15℃ and refrigerator 4℃). The results show that phenobarbital in preserving blood was decomposited very slowly. There was almost the same decomposition speed under the preserving conditions. The results supply a reference data for estimating poison analytical result in doubting poison case by phenobarbital.