The　high　viscosity　of　heavy　oil　made　it　difficult　to　exploit　and　transport　heavy　oil　in　pipeline.　In　this　research,　N-[(2-hydroxy-3-trimethylammonium)　propyl]　O-stearoyl　chitosan　tetraphenylboride　(sc-CTS-st)　was　synthesized　from　chitosan,　2,　3-epoxy-propyl　trimethyl　ammonium　chloride,　sodium　tetraphenylboron　and　stearyl　chloride.　sc-CTS-st　contains　long　chain　saturated　aliphatic　hydrocarbon,　hydroxyl　group　and　benzene　ring,　which　could　be　dissolved　in　heavy　oil　fully　and　interacted　with　asphaltene.　At　50　degrees　C,　the　viscosity　of　heavy　oil　could　be　reduced　to　13,800　mPa　center　dot　s　at　most,　with　a　viscosity　reduction　rate　of　57.54　%.　SEM　and　XRD　showed　that　sc-CTS-st　could　affect　the　supramolecular　accumulation　structure　of　asphaltenes.　Using　FT-IR,　sc-CTS-st　could　interact　with　asphaltene　in　the　form　of　hydrogen　bonds　using　the　polar　parts　of　the　molecule,　thereby　weakening　the　self-association　between　asphaltene　molecules.　Molecular　simulation　was　used　to　demonstrate　the　interaction　mechanism　between　chitosan　derivatives　and　asphaltenes.　sc-CTS-st　interacted　with　asphaltene　through　chemical　bonding　and　influenced　the　self-association　of　asphaltene　molecules.　In　addition,　the　non-polar　portion　of　sc-CTS-st　molecules　could　form　a　coating　on　the　outside　of　the　asphaltenes　stacking　structure,　thus　shielding　or　reducing　the　polarity　of　the　stacking　structure　surface.