Abstract: The authors prepared mono-dispersed water-in-oil emulsions by polymer microchannel(MC) emulsification method, and investigated the effects of various parameters on preparation characteristics of the emulsion. Results show that the pressure of the dispersed phase, viscosity of the continuous phase, and type of emulsifier affect significantly the preparation characteristics of the emulsion. Average droplet diameter and coefficient of variation(CV, less than 10%) increase as the pressure of the dispersed phase increases in pressure ranges for stable droplet formation, and when the pressure of the dispersed phase are more than critical pressure P_max or less than critical pressure P_min, the mono-dispersed emulsions are not created. Average droplet diameter and CV increase with the increasing viscosity in the continuous phase. On the other hand, mono-dispersed water-in-oil emulsions with average droplet diameters of 42 to 60 μm(CV less than 10%) are prepared successfully using tetr-aglycerin condensed ricinoleic acid ester as the emulsifier, droplets are created from MC, but they flocculated or coalesced immediately when using glycerin monooleate and lecithin as the emulsifiers, the surface of the MC plate is wetted and the dispersed phase flowed out continuously through the MC when using proteins as the emulsifiers.