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　°C,　the　viscosity　of　heavy　oil　could　be　reduced　to　13,800　mPa·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.　©　2023　Elsevier　B.V.