A theoretical study on the rate of adsorption of a biocolloidal particle. onto a charged surface is investigated. Here, both a particle and a surface are immersed in an electrolyte solution. A biocolloid is imitated by an ion-penetrable membrane carrying a nonuniformly distributed fixed charge on a rigid core. The effects of sizes of charged species, including cations, anions, and fixed charge, were taken into account to more realistically reflect a colloidal system. The results of numerical simulations reveal that, based on a constant amount of fixed charge in the membrane layer, the classical point-charge model predicts a faster rate of adsorption than the present model does. The greater the nonuniformity of the fixed charge, the longer the time required for biocolloidal adsorption. A nonlinear distribution of fixed charge results in a slower rate of adsorption than a linear one does in general. Thin membrane thicknesses, high average concentrations of fixed charge, low permittivity of the medium, and large sizes of cations, anions and fixed charge produce slow rates of adsorption. The influential order of the sizes of charged species for the adsorption rate is (size of fixed charge) > (size of anion) > (size of cation).