The interaction between a cationic porphyrin and bovine serum albumin (BSA) was studied by using surface plasmon resonance (SPR) spectroscopy, which was combined with fluorescence quenching method and cyclic voltammetric method to confirm the binding kinetic results. In this paper, the SPR method used to study the drug-protein interaction was described in detail. The association rate constant, dissociation rate constant and the equilibrium association constant of porphyrin binding to BSA obtained from this method were 1067 ± 18.23 M(-1) s(-1), 0.01644 ± 0.00012 s(-1), and 6.49 × 10(4) M(-1), respectively. The equilibrium association constants obtained from the fluorescence quenching method and the cyclic voltammetric method were 1.102 × 10(5) M(-1) and 1.21 × 10(5) M(-1), respectively.