Since the traditional processing methods cannot solve the problem of poor quality and low efficiency of PMMA micro-channel processing,the ablation mechanism and process parameters of preparing PMMA microchannels with ultrafast laser direct-writing were studied in this paper.The effects of laser power,processing speed and processing times on the width and cross-section of the micro-channel were analyzed based on experiments.The microchannels were fabricated by ultrafast laser processing system,and the surface morphology of the microchannels were observed by three-dimensional microscopy(VHX-5000).The experimental results show that when the processing speed of ultrafast laser is 20 mm/s and the laser power is 1.5 W,the width of the microchannels are smaller and the trend of the width is relatively stable.When the number of times of ultra-fast laser acting on PMMA is the same,the width of the prepared microchannels and the processing speed of the laser increase linearly as the processing speed increases gradually.When the processing speed is higher,the width of the microchannels is smaller and the wall trend is relatively flat.However,when the processing speed is constant and the output power of ultrafast laser is 1.5 W,the phenomenon of residue accumulation and bubble bulge is not easy to occur in the inner wall of microchannels.In this paper,by optimizing the technological parameters of ultrafast laser processing system,microchannel chips with high dimensional accuracy,smooth surface and width of about 20~90 μm are fabricated.