In this paper, a discussion and an optimizing numerical analysis of the penetration and attenuation of the thermonuclear tokamak plasma fueling by the supersonic cluster molecular beam(SMB) has been presented.The cluster formation and dissolution,SMB adiabatic expansion,shielding and cooling effect are all taken into account.An optimized numerical model is applied in the analysis and shown to be in good agreement with the experimental observations.The possibility for fueling large tokamak plasmas with SMB injection is explored.