The　preparation　of　electrospinning　air　filtration　membranes　based　on　fully　bio-based　materials　is　the　key　to　alleviate　the　energy　and　environmental　crises.　However,　for　the　lack　of　reasonable　materials　matching　and　structural　design　strategies,　it　is　difficult　to　balance　the　mechanical　and　filtration　properties　of　bio-based　fiber　membranes.　In　this　study,　ethyl　cellulose　(EC)/chitosan　(CS)　bimodal　nanofiber　membrane　was　prepared　by　one-step　electrospinning.　In　detail,　EC　was　intended　to　construct　a　low　binding　energy　system　while　CS　was　introduced　to　enhance　split.　And　the　ethanol　and　water　were　used　as　solvents.　More　importantly,　the　“internal-external　synergistic　enhancement　strategy”　was　proposed　creatively:　on　the　one　hand,　the　hydrogen　bonding　was　enhanced　for　the　incorporation　of　CS;　on　the　other　hand,　bonding　structures　were　formed　among　the　fibers　after　the　heating-annealing　process,　which　was　attributed　to　the　melting　and　solidification　of　CS.　The　combination　of　hydrogen　bonding　and　bonding　structures　dramatically　improved　the　mechanical　properties　of　the　membrane.　The　elastic　modulus　and　tensile　strength　of　the　15EC/1.5CS　membrane　were　103.13　and　5.97　MPa.　At　85　L/min,　the　filtration　efficiency　of　15EC/1.5CS　membrane　for　PM0.3　was　99.01　%,　the　pressure　drop　was　only　56.2　Pa,　and　the　quality　factor　was　0.082　Pa−1.　©　2025　Elsevier　B.V.