The　droplet　ejection　technology　based　on　electrohydrodynamic　(EHD)　method　can　produce　micro-droplets　smaller　than　the　diameter　of　the　nozzle,　which　is　a　technical　option　to　improve　the　resolution　of　inkjet　printing　and　alleviate　the　risk　of　nozzle　blockage.　However,　EHD　ejection　is　affected　by　many　parameters　including　the　flow　rate,　the　voltage　between　the　nozzle　and　the　collector　electrode.　It　is　of　practical　value　to　monitor　the　state　of　the　EHD　ejection　in　real-time.　In　this　paper,　an　EHD　ejection　device　is　built,　which　include　a　high-speed　camera,　a　current　amplifier　for　the　induced　current　at　the　collector　electrode,　and　an　optical　particle　counter.　Through　high-speed　photography　and　image　processing,　detailed　information　of　the　ejection　process　can　be　obtained.　But　the　equipment　is　expensive,　and　real-time　processing　of　large　amount　of　images　are　impossible.　Combined　with　the　measurement　of　the　induced　current　at　the　collector　electrode　and　the　scattered　light　of　the　micro-droplet,　a　rather　complete　description　of　the　ejection　state　can　be　obtained.　This　approach　is　expected　to　be　used　for　the　monitoring　and　control　of　the　EHD　ejection.　©　2020　IEEE.