Abstract Aim: To study the effects of propyl gallate on the interaction of tumor necrosis factor-α (TNF-α) with its soluble receptor, sTNFR-I. Methods: Interactions between TNF-α and sTNFR-I were analyzed using an IAsys biosensor. sTNFR-I was immobilized on the carboxymethyl dextran (CMD) surface of the IAsys biosensor cuvettes, and TNF-α preincubated with different concentrations of propyl gallate was added to the cuvettes. The resonant angle shift caused by the binding between TNF-α and sTNFR-I was then recorded. Results: sTNFR-I was immobilized on the CMD surface at a density of 2.76 ng/mm2. TNF-α then bound the immobilized sTNFR-I specifically, and propyl gallate was able to enhance the binding between TNF-α and sTNFR-I in a dose-dependent manner. Conclusion: The binding between TNF-α and sTNFR-I is one of the targets that propyl gallate can act on in vivo. The IAsys biosensor offers a new clue as to the study on the mechanisms of action of propyl gallate.