High-performance frontal analysis (HPFA) was used for the determination of the binding constant of Sibuprofen to human serum albumin (HSA). This experiment was based on an Inertsil 100 Diol 5 column and sodium phosphate buffer (pH 7.4 and ionic strength of 0.17) as the mobile phase. The mixture of S-ibuprofen and HSA (70 $mu$M) solution were directly injected into the HPFA column. An injection volume of 200 $mu$L and a “estricted injection”method were applied to ensure the drug to be eluted as a zonal peak with a plateau. The unbound drug concentration was calculated from the peak height of the zonal peak. Scatchard analysis was used for evaluation of the binding constant (K) and binding affinity (nK) of S-ibuprofen to HSA, and the results were K = 2.833 ${ imes}$ 10$^4$ [L mol$^{-1}$], nK = 4.935 ${ imes}$ 10$^4$ [L mol$^{-1}$], respectively.