Sample　deposition　based　on　micro-droplet　ejection　has　broad　application　prospects　in　the　field　of　biomedicine.　Ejection　of　RPMI-1640　culture　medium　(without　cells)　is　investigated　experimentally　using　a　home-build　electrohydrodynamic　(EHD)　ejection　system,　consisting　of　a　liquid　supplier　and　a　nozzle,　a　voltage　source,　a　droplet　collector,　and　a　supplemented　photoelectric　monitoring　module.　Electric　voltage　is　applied　between　the　nozzle　and　the　droplet　collector.　The　liquid　surface　is　electrically　charged　and　the　ejection　takes　place　when　electric　force　overcomes　the　surface　tension.　At　appropriate　voltages,　uniform　ejection　states　are　established　with　ejection　frequency　ranging　from　a　few　to　a　few　tens　of　Hertz.　Monitoring　of　the　ejection　process　is　performed　by　two　methods.　The　ejection　process　can　be　recorded　by　a　high　speed　camera,　and　then　analysed　by　image　processing.　Using　output　signal　of　a　charge　amplifying　circuit　as　a　reference,　a　single　shot　camera　is　controlled　to　capture　images　at　certain　delays,　anti　the　entire　process　of　the　droplet　ejection　can　be　recorded.　Experiments　have　shown　that　when　the　liquid　meniscus　breaks　up,　the　output　signal　of　the　charge　amplifier　reaches　the　maximum.