Abstract: The effect of high pressure processing on the activity and conformation of inulin fructotransferase (IFTase) were investigated with high performance liquid chromatography, fluorescence spectroscopy and circular dichroism, moreover the relationship between enzyme conformation and enzyme activity after high pressure processing (HPP) was analyzed. The results showed enzyme activity after HPP increased firstly and then decreased with elevated pressure and extended dewell time at 80℃. The relative enzyme activity at 200MPa for 30min was the maximum and reached 124. 08%. Trp residues contributed to intrinsic fluorescence of IFTase. The positive linear correlation between relative enzyme activity and relative fluorescence intensity indicated enzyme activity had some connection with microenvironment changed by pressure. The results of circular dichroism spectrum showed IFTase had only one characteristic negative peak at 219nm, moreover, the value of characteristic negative peak at 219nm and relative enzyme activity presented a negative linear correlation, which indicated β - sheet was the structural base of IFTase for catalytic activity. The study of conformation changed by pressure would provide some theoretical evidences about high pressure enhancement of enzyme.