Abstract: A freezing analytic system for extracting tissue free water tritium (TFWT) in biological sample was designed and processed. The results show that while 20 g leaves of Yunnansan sample extracting time is 5-6 h in this system, the extracting water of sample is 4-5 mL, and the average extracting ratio of TFWT is 61%. This analytic system can apply to measurement of TFWT in biological sample.