Abstract: In order to investigate the best determination methods for organically bound tritium (OBT) activities, the plant samples in the vicinity of Qinshan nuclear power base and the plant samples intentionally contaminated were collected. The most suitable volume of immersion water and immersion time to extract most exchangeable organically bound tritium (E-OBT), the effect of tritium residue during combustion of dry plant samples and collection of combustion water were studied. The results show that the most suitable mass proportion between immersion water with low-level activity tritium and dry sample is 30 times, and the immersion time is 24 h for the effective elimination of E-OBT by isotopic exchange. The tritium residue in combustion apparatus is completely cleared with 50 mL water. There is no tritium residue in the collection bottle of OBT and quartz boat after washing 3 times with large volume of water.