A useful approach for determining the binding ability which occurres in a protein-small molecule system was studied by a method of dynamic dialysis utilizing a hollow fibre unit. A dependency on experimental variables in the absence of protein was examined in order to characterize the nature of the dialytic process. It was shown that the rate of small molecule escaped across the dialytic membrane was dependent on stirring or flowing rate, temperature and pH, but independent on buffer strength or viscosity. The protein binding ability was examined by means of comparing amounts of small molecules in the absence and presence of protein. Kinetic parameters for the binding behaviour analysed from the Scatchard plot in the present experiment were in agreement with values previously reported.