Abstract: This paper investigates the design and fabrication process of micro-droplet chips based on micro-milling technology, with emphasis on optimizing microchannel structures and machining processes. Taking the basic Y-shaped channel as the research object, three microchannel structures are designed and screened. Droplet-generation experiments are conducted to verify their capability of producing continuous and stable droplets at channel corners, and the chips are accordingly fabricated. Experimental results indicate that micro-milling is applicable for machining microchannels on PMMA. The cross-sectional dimensions of microchannels are affected by tool size, machining parameters and material properties. Compared with photolithography, micro-milling possesses the advantages of low cost and high flexibility. The chip structure is designed in UG software and CAD drawings are exported. Tool paths and machining parameters are configured in Autodesk Artcam Premium 2018. The generated program is transmitted to processing equipment, and micro-milling cutters are adopted to machine PMMA plates. Key parameters including spindle speed and feed rate are optimized through analyzing the surface roughness of microchannels, so as to determine stable process conditions. After the chips are manufactured, two fluids with different densities are injected into respective microchannels for droplet-generation tests. The high-density fluid encapsulates the low-density fluid to form independent and continuous droplets, and the micro-droplet chip structure with optimal performance is finally selected. This research provides theoretical basis and practical references for the efficient and low-cost fabrication of micro-droplet chips.