In　the　process　of　exploration　and　development　of　oil　and　gas　fields,　the　acidic　environment　of　oil　reservoir,　production　and　transport　processes　cause　corrosion　of　pipelines　and　equipment,　resulting　in　huge　economic　losses　and　production　safety　risks.　Corrosion　inhibitors　were　widely　used　in　oil　industry　because　of　simple　operation　process　and　economical.　In　this　study,　three　environmentally　friendly　corrosion　inhibitors　were　synthesized　based　on　the　natural　polysaccharide　chitosan.　Corrosion　inhibition　of　three　dendritic　chitosan　derivatives　(We　name　them　BH,　CH　and　DH)　on　mild　steel　in　1　mol/L　HCl　solution　with　natural　ventilation　system　was　evaluated　by　weight　loss　experiment,　electrochemical　analysis　and　surface　morphology　characterization.　The　experimental　results　showed　that　when　the　three　dendritic　chitosan　derivatives　added　in　the　corrosive　medium　were　500　mg　L-1,　the　corrosion　inhibition　efficiencies　were　all　more　than　80%.　Based　on　quantum　chemical　calculation,　inhibition　mechanisms　of　three　dendritic　chitosan　derivatives　were　investigated　according　to　molecular　structures.　The　results　showed　that　the　benzene　ring,　Schiff　base　and　N　atom　contained　in　the　molecule　were　the　active　centers　of　electron　exchange,　which　were　more　likely　to　form　a　film　on　the　carbon　steel　surface,　thereby　slowing　or　inhibiting　corrosion.　The　results　also　predicted　the　corrosion　inhibition　effect　BH　＞　DH　＞　CH,　which　was　consistent　with　the　experimental　conclusion.　(c)　2023　The　Authors.　Publishing　services　by　Elsevier　B.V.　on　behalf　of　KeAi　Communications　Co.　Ltd.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(http://creativecommons.org/licenses/by-nc-nd/4.0/).