Fine-tuning　of　the　physical　stacking　structure　for　microporous　polyimide　(PI)　membranes　via　the　stretching　processing　is　a　practical　way　of　achieving　advanced　membrane　materials　with　improved　aging　resistance　as　well　as　high　gas　separation　performance.　Here,　a　fluorinated　polyimide　6FDA:BPDA-TFDB(1:1:2)　is　used　as　a　prototype　and　a　series　of　stretched　membranes　X%-PI　are　fabricated　by　uniaxially　stretching　the　membrane　to　different　elongation　ratio　and　then　annealing.　Based　on　birefringence　and　wide-angle　X-ray　diffraction　measurements,　it＇s　found　that　regular　orientation　of　polymer　chains　along　the　stretching　direction　and　fine-tuning　of　d-spaces　from　interchain　packing　and　π-π　stacking　happen　during　the　uniaxial　stretching　process.　As　such,　compared　to　pristine　PI　membrane,　the　stretched　membranes　show　better　mechanical　and　thermal　stability,　especially　for　the　one　with　higher　stretching　ratio.　In　addition,　owing　to　the　increased　packing　density　of　polymer　chains,　the　highly　stretched　membrane　of　40%-PI　shows　significantly　improved　gas　perm-selectivity　by　32.8%,　24.3%,　and　12.6%　for　He/CH4,　H2/CH4,　and　CO2/CH4　gas　pairs,　respectively,　in　comparison　to　pristine　membrane.　Furthermore,　40%-PI　exhibits　much　higher　gas　permeability　retention　rate　than　that　of　other　membranes　after　three　months＇　aging.　We　expect　that　this　work　can　offer　polymer　materials　processing　guidance　for　the　preparation　of　high-performance　gas　separation　membrane　in　future.　©　2023　Elsevier　B.V.