Abstract: In order to understand the petal extension mechanism，both FTIR（fourier transformation infrared spectroscopy）and Guassian multi-peak fitting were used to explore spectrum properties and protein secondary structure differences of Paeonia ostii‘Fengdanbai’petal at the flower-bud，initiating bloom and bloom periods. The main results were as follows：The peak intensity at 777，1 105，1 155，1 243，1 447，1 651，1 740，2 853 and 2 926 cm-1 were enhanced in sequence with flowering，indicating that the metabolism products such as phospholipids，nucleic acids，lipids，proteins were increased during the process of flowering. A shift from 1 030 cm-1 to 1 060 cm-1 was observed in petal at flower-bud period and bloom period，which showed that cell wall polysaccharides of petal were glucomannan and arabinan，respectively. As compared with the petal at flower-bud period，the number of methyl groups in protein（A 2 951 cm-1/A 2 858 cm-1）of petal decrease by 7.97% and 13.38% at initiating bloom period and bloom period，respectively. The variation in glycoprotein of the samples（A 1 083 cm-1/A 1 547 cm-1）showed a downward trend after flowering，it could speculate out that protein regulate the petal extension by glycosylation in‘Fengdanbai’. The result of Guassian multi-peak fitting for the amideⅠregion（1 600–1 700 cm-1）indicated that the petal contained β-sheet + side chain + pectin，β-sheet，random coil，α-helix and loop + turn of secondary protein structure at different stages. And the α-helix，β-sheet and random coil showed an increase trend after flowering. The result indicated that the presence of low amounts of α-helix domains in petal at flower-bud period might compensate for reducing protein-water hydrogen band caused by lack of water. And also ATP was modified，which would provide the material base for petal-extension. The protein would regulate the complex biochemical processes in petal extension by forming more functional domains. The research results provided theoretical references for the substance change and the protein regulation on extension mechanism of petal.

Key words: Paeonia ostii‘Fengdanbai’, petal, fourier transformation infrared spectroscopy（FTIR）, Guassian multi-peak fitting, protein secondary structure