Abstract: Micro flow-focusing devices were widely used in the synthesis of particulate material, drug packaging, cell culture and other areas owing to the convenience and effectiveness to produce highly monodisperse and precisely sizecontrollable droplets. To optimize the channel structure and geometry parameters deeply is of benefit to achieve the precise regulation of droplets' diameter, uniformity and the size ranges. For the adaptive design, channel depth, orifice length and the angle in continuous and discrete phase are taken into account to investigate the influence of geometry configurations on the microdroplet diameter and its generated cycle stages in flow focusing microchannel by making use of numerical simulation. It is shown that the droplet diameter approximately increases linearly with the channel depth, meanwhile, when the channel depth is less than 30 μm, the droplet's cycle increases suddenly under the application of strong capillary force. The microdroplet diameter and its cycle are both the shortest while the angle of the continuous phase and discrete phase θ is nearly 90°, and too large or too small angles are both not conductive to generate droplets with uniform diameter and well controlled particle size. Orifice length is used to adjust the alteration of the microdroplet diameter and its cycle, which lead to the average rangeability within 3%~5%. In addition, the width of orifice region is an important factor a ecting the microdroplet diameter and its cycle in cross microchannel. When the channel depth is fixed, the wider the orifice region is, the greater the microdroplet diameter and its cycle are.