Abstract: By using bioinformatics methods and tools， the physical and chemical properties， transmembrane， hydrophobicity and hyrdrophilicity， secondary structure and tertiary structure of extensin protein of Betula phatyphylla were analyzed and then compared with other species in this paper. The result showed that the molecular formula is C680H1099N195O195S11. Extensin protein is hydrophilic and not transmembrane protein， whose main component is α\|helix and random coil and similar to Populus nigra.

Key words: Betula phatyphylla, extensin, bioinformatics