In　this　study,　black　phosphorus　quantum　dots　(BPQDs)　are　synthesized　by　improved　ultrasonic-assisted　liquid　exfoliation.　The　as-prepared　BPQDs　are　deposited　on　large-area　conductive　substrates　by　electrophoretic　deposition,　and　exhibit　high-sensitivity　humidity　sensing　and　excellent　electrical　properties.　The　results　offer　not　only　a　facile　and　efficient　method　to　synthesise　stable　BPQDs　films,　but　also　a　new　opportunity　to　develop　humidity　sensors　and　nano-electronic　devices.