In view of the problems of the inflatable seal shroud in the existing wind tunnels,the design scheme for a new type flexible wall seal shroud with a concave construction was put forward.The designed inflatable sealing shroud can be separated from the contact with the side wall in the natural state,so as to ensure that the inflatable sealing shroud does not scratch the side wall and improve the service life of the sealing shroud.The concave crosssection is adopted,which can ensure that the inflatable sealing shroud has enough expansion,so as to realize the sealing between the flexible wall and the wind tunnel side wall.Through airtightness test,expansion/retraction test,innersealing test of fixture,explosion pressure test,gasfilled fatigue test and wind tunnel test,the new inflatable seal shroud was validated,and was applied successful in the new transupersonic wind tunnel.It is proved by practice that the new inflatable seal shroud has compact structure,reliable sealing performance and long service life.