Abstract: Many proteins involve fruit ripening，of which a class of protein called expansin is a new diseovered member．During fruit ripening modification of the primary cell wall is required． Expm~in， without enzyme activity．but has been shown to promote cel wall loosing． There are evidences expansin binding in cellulose mi·crofibrils disrupting the hydrogen bonds formed with xyloglucan during fruit ripening． In order to let more people to know the new aIea， its cutrent status and developing trands were reviewed ． Th e discovery， mechanism， gene familv and function of expansin were introduced ．Th eir role in the fruit ripening was discussed． Correlation wi the cell wall enzymes of expansin was suggested． New strategies using transgenic technology to regulate fruit ripening were proposed．

Key words: Expansin, Function, Fruit, Ripening, Softening