Abstract: The generation of droplets in co-flow was studied by the level set method. Taking into account liquid-liquid two phases， the dispersed phased liquid is a mixture combined paraffin oil with heptane， whereas， the continuous phase fluid is aqueous water. Herein， these calculated works were carried out with inlet velocity and viscosity of the dispersed phase fluid， as well as injected hole size. When the dispersed phase fluid with velocity from 15mm/s to 48mm/s flows into a hole channel with radius of 1mm， the jetting height increases and the periodic generation reduces as the inlet velocity increases gradually. Meanwhile， increasing its viscous coefficient could decrease the disinfected time between droplet tension and drug force， so that frequency was increased and homogeneous characteristics were improved. The velocity of laminar flow was directly affected by the size of the hole. Owing to shrink the hole size， the sharpness of injected velocity occurs， resulting in the smaller size of the extruded droplet.

Key words: microfluidics, droplet, level set method, co-flow