With　the　development　of　national　defense　equipment　and　the　aggravation　of　population　aging,　the　demand　of　lower　limb　flexible　exoskeletons　for　battlefield　soldiers,　army　logistics　and　the　elderly　population　has　risen　sharply.　Based　on　this　urgent　demand,　a　portable　ankle　assistance　Exosuit　system　with　good　wearability,　high　human-machine　compatibility　and　excellent　assistance　performance　has　been　developed.　According　to　the　physiological　characteristics　of　the　ankle　joint　and　the　parameters　of　lower　limbs,　the　ergonomic　design　and　development　of　the　Exosuit　body　and　driving　unit　are　achieved　where　the　driving　unit　is　placed　at　the　waist　to　reduce　the　added　mass　of　legs　and　feet　as　much　as　possible.　Based　on　the　biological　torque　of　the　ankle　joint,　the　model　of　expected　auxiliary　force　is　established.　The　system　stiffness　of　the　assistance　Exosuit　and　local　soft　tissue　is　obtained　by　the　experimental　measurement.　Then　the　established　model　is　transformed　into　the　displacement　model　of　the　driving　unit.　Based　on　the　gait　periodicity　of　lower　limbs,　a　controller　with　iterative　learning　control　algorithm　as　the　core　is　designed　to　track　the　force　model　through　iteratively　learning　the　output　errors　of　historical　time.　In　order　to　evaluate　the　assistance　performance　of　the　Exosuit　system,　the　degree　of　muscle　activation　and　fatigue　changes　were　analyzed　by　measuring　the　EMG　signals　of　the　plantarflexion　muscles.　Under　the　condition　of　Power-ON,　the　degree　of　muscle　activation　under　three　walking　speeds　decreased　significantly,　especially　lateral　gastrocnemius　muscle.　The　muscle　activation　degree　of　the　medial　gastrocnemius　muscle　decreased　by　an　average　of　9.62%　±　1.12%.　The　absolute　value　of　the　change　slope　of　mean　power　frequency　(MPF)　and　median　frequency　(MF)　descended　obviously.　Hence,　the　rate　and　degree　of　muscle　fatigue　decreased　and　the　walking　endurance　of　lower　limbs　increased.　©　2023　Editorial　Office　of　Chinese　Journal　of　Mechanical　Engineering.　All　rights　reserved.