A key issue for theoretically predicting the aggregation rate of colloidal particles is to appropriately describe interparticle interactions. The recent progress in the study of interaction potential between suspended particles is the introduction of the structured-layer potential (SLP). However, the published data still show the degree of approximation of the theoretical expectation varies with the particle size, which means that the relevant parameters of SLP may not be constant independent of particle size. In this study, the approximation degree of the theoretical model to the experimental data of aggregation rates of particles with different sizes under different interparticle interaction parameters was compared. The results demonstrated that, in all cases of rapid and slow homo-aggregation and hetero-aggregation, the theoretical value of aggregation rates using particle-size-dependent SLP parameters are much closer to the experimental value than that using particle-size-independent SLP parameters.