Abstract: Thermal analysis is a kind of technology in which the relationship between physical natures of material and-temperature is continuously measured in an automatical way under temperature controlling program. We choose the seeds of pinaceae and taxodeaceae as research material of tree classification. We found that they had the same characteristic peak and were different on thermal cracking gas chromatograph chart and DTA chart. Similarly, there were certain analogy and differences among the same genus of different species. Thermal analysis methods not only can be used in tree classification but also supply much messages for taxonomy.