Self-assembly gold nanocrystals (Au-NCs) are formed on the surface of single-walled carbon nanotubes (SWNTs) on a platform of field-effect transistors by electron-beam evaporation and post-rapid thermal annealing processes. Strong oscillations in the SWNT channel (approximately 2000 nm long) current occur below 150 K. The Raman scattering from the SWNTs suggests that the electronic structure of the SWNTs has been significantly altered by the strong Coulombic interaction with the attached Au-NCs. Two possible mechanisms are presented to explain the observations: (1) the charging process of Au-NCs is dominated by the Coulomb blockade effect. Thus the electrostatic potential of the charged Au-NCs modifies the Schottky barrier at the SWNT/Au electrode contacts, and subsequently affects the SWNT channel current (or the Schottky barrier modulation) and (2) the charged Au-NCs serve as scattering centers, which modify the local potential along the SWNT channel and then induce the oscillations in the current (i.e. energy band modulation).