Micro scale 3D printing based on electrohydrodynamic (electrohydrodynamic jet printing, E-jet printing) is an emerging and promising micro/nano scale 3D printing processes, which was demonstrated with outstanding strengthens and high potentials in terms of high resolution, low cost and easy operation. Micro scale 3D printing was utilized in various areas, including tissue engineering, electronics, micro fuel cell, composite materials, etc. Different from the traditional jet printing technology, the EHD jet is driven by electric field to draw a very fine jet from the top of the liquid cone. The forming mechanism of micro scale 3D printing based on EHD was complex, and there were several influencing factors and process parameters. The stress state of Taylor cone was analyzed theoretically, and then the finite element simulation and experimental methods were used to verify the theory. Through the investigation, the jetting mechanism of the micro scale 3D printing method was explored, and the influences of voltage and pressure of cone-jet mode on E-jet printing were revealed, and some useful conclusions were achieved. The result showed that the Taylor cone was shortened with the increase of voltage, and it was lengthened with the increase of inlet. Meanwhile, it was shown that the printing can be carried out in a certain range of voltage and pressure, rather than specific values of voltage or pressure, so the cone jet and printing quality can be improved by adjusting the voltage and air pressure. A printing example of light curing resin material was given, and the printing quality was good. The research results provided theoretical basis and guidance for improving the forming accuracy and control performance of micro scale 3D printing based on EHD.