In this paper the interaction between trelagliptin succinate (QGLT) and bovine serum albumin (BSA) was studied by fluorescence spectrometry. The factors affecting fluorescence quenching such as solution acidity and medium characteristics were optimized. The examination results of quenching mechanism showed that the fluorescence intensity of BSA was quenched strongly by QGLT mainly through a static quenching procedure, the number of binding sites was 1, and the biding constants was 4.529×104L·mol－1 (298　k) or 2.958×104 L·mol－1 (303　k), respectively. The determination results of thermodynamic parameters show that the change of Gibbs free energy, enthalpy or entropy was negative, which clarified there was an automatic reaction happened between QGLT and BSA, and both hydrogen bonds and van der Waals force played a role in the binding of QGLT to BSA. It was also found in the examination that Lineweaver-Burk equation ［(F0－F)－1=2.711×10－4+3.51×10－3 cQGLT－1(cQGLT: 0.5～10.0　μg·mL-1)］ owned better linear relationship (r=0.998　9) with the detection limit of 0.13 μg·mL-1.　The recovery experiment results showed that the method owed good accuracy(the recovery is 94.0%～97.5%) and the proposed method has been successfully applied to determine QGLT in QGLT tablet and human serum. The examination developed a new method to determine the content of QGLT.