Inspired by the structural and functional attributes of Cell-penetrating peptides (CPPs), in this study, diverse cationic and hydrophobic amino acids (AAs), which are regarded as the essential sequence of CPPs, were adopted to functionally modify chitosan (CS) to further enhance drug absorption across lung epithelial cells, and explore the absorption enhancing mechanism of different AA categories. Here, taking octreotide as a drug model, multifarious amino acids decorated chitosan copolymers (AA-CSs) were synthesized to investigate the influence of biomimetic AA-CSs structure on drug transmembrane absorption utilizing both 3D Transwell cell models and Sprague Dawley rats. It was demonstrated that indeed the absorption enhancing action of AA-CSs was AA categories-dependent. In comparison to native CS, hydrophobic AA-CSs induced no obvious enhancement in transmembrane permeation, while cationic AA-CSs improved drug absorption across pulmonary epithelium to varying degrees, with the highest enhancement ratio observed for arginine-CS (Arg-CS) group. Mechanism studies indicated paracellular pathway-mediated drug transport of AA-CSs. The in vivo pharmacokinetic data from microparticle groups revealed the AA categories-dependent absorption enhancing effect. In conclusion, the absorption enhancing activity of AA-CS copolymers depends on their AA categories, the enhancement extent of cationic AAs, particularly arginine, is preferable than that of hydrophobic AAs.