Abstract: The latest progress of the extensive and in-depth studies on electrospray ion source(ESI) was tentatively reviewed.The discussions with specific examples centered on:i) The operating principles and modeling of emitted charged droplets from Taylor cone,including the evaporation model,charged residue model and chain ejection model; ii) The influence of major factors,including but not limited to the ionization voltage,liquid flow-rate,auxiliary gas,temperature,emission tip position,analyte properties and interface design,on the yield of ion,sensitivity,signal-to-noise ratio,and sampling efficiency of ESI mass spectrometry; and iii) Optimization of structural design and operation conditions of ESI.In addition,the existing problems,possible solutions,development trends of theoretical and experimental studies,and potential applications of ESI mass spectrometry were also briefly discussed in a thought provoking way.