The diffusion coefficients** of l-lysine hydrochloride and l-arginine hydrochloride in their aqueous solutions at 25 degrees C were determined by the metallic diaphragm cell method which is characterized by accuracy, promptness and convenience. Meanwhile, the densities and viscosities of the solutions were also determined. Based on all these data a semi-empirical model for correlating the diffusion coefficients of solid organic salts in their aqueous solutions at 25 degrees C was proposed. The fitting result of this model is comparatively satisfactory. Compared to a former model, Gordon Model, this model can avoid a number of difficulties and arduous work.