In　this　paper,　the　special　flow　phenomena　such　as　condensation,　re-evaporation　and　choking　in　the　transonic　mixing　process　of　steam　ejector　are　captured　using　visualization　technology　with　the　high-speed　camera.　Analysis　and　discussion　mainly　focus　on　the　formation　mechanism　of　each　special　flow　phenomenon　and　the　flow　characteristics　of　condensation　flow.　The　results　reveal　that　there　are　many　condensation　droplets　of　dynamic　imbalance　in　the　primary　steam　jet.　The　entrained　steam　is　being　chocking　at　the　end　of　the　mixing　chamber　where　large　numbers　of　condensation　droplets　are　generated　simultaneously,　and　then　the　condensation　droplets　are　quickly　spread　out　toward　both　sides　attached　against　the　wall.　The　condensation　flows　downstream　the　choked　cross-section　will　be　re-evaporated　many　times　until　a　rather　stable　wet　steam　flow　is　formed,　and　then　introduce　into　the　diffuser.　The　condensation　flows　upstream　merge　with　the　near-wall　condensation　droplets　thrown　out　from　the　wet　steam　jet,　and　then　a　membranous　condensation　flow　and　clockwise　circumferential　flow　are　produced　in　the　front　of　the　mixing　chamber.　There　are　certain　of　accumulation,　oscillation　and　other　complex　flow　characteristics　of　the　condensation　flows　near　the　entraining　entrance.　The　formation　of　condensation　flows　will　partly　reduce　the　effective　flow　area　and　hinder　the　smooth　flow　of　entrained　steam　in　the　tapered　channel.　©　2019,　Science　Press.　All　right　reserved.