Janus　particles　with　asymmetric　crystals　show　great　importance　in　optoelectronics　and　photocatalysis,　but　their　synthesis　usually　requires　complicated　procedures.　Here,　an　unexpected　Janus　vitrification　phenomenon　is　observed　in　a　droplet　caused　by　the　Leidenfrost　effect　at　a　cryogenic　temperature,　which　is　commonly　regarded　as　symmetric.　The　Leidenfrost　phenomenon　levitates　the　droplet　when　it　comes　in　contact　with　liquid　nitrogen　causing　different　cooling　conditions　on　the　droplet＇s　top　and　bottom　surfaces.　It　induces　asymmetric　crystallization　in　the　droplet,　forming　a　Janus　vitrified　particle　with　an　asymmetric　crystallization　borderline　after　cooling,　as　further　evidenced　by　cryotransmission　electron　microscopy　(cryo-TEM)　experiments.　Theoretical　analysis　and　experimental　study　indicate　that　the　position　of　the　asymmetric　crystallization　borderline　is　determined　by　the　droplet　radius　and　density,　and　the　observation　window　of　asymmetric　crystallization　borderline　is　determined　by　the　chemical　concentration.　The　finding　reveals　the　asymmetric　crystallization　phenomenon　in　droplet　vitrification　for　the　first　time,　and　provides　a　new　insight　for　creating　Janus　particles　through　the　Leidenfrost　phenomenon.