Abstract: The Scheutjens - Fleer model on monodisperse polymer adsorption was extended to the situation of polydisperse polymer adsorption by the method of seeking the extremum of the partition function constructed for the system. Using a suitable calculation method, the authors obtained the numerical re-suits of the model which had been very difficult to solve before. The microscopic adsorption of the poly-disperse polymer at solid/liquid interface, the effects of the polydisperse index on the properties of the adsorption layer and the size distributions of train, loop and tail conformations were studied. It is shown that a polymer with a large molecular weight is adsorbed more favorably and that the polydisperse index affects the adsorption of polydisperse polymer largely.