ITO thin films have excellent electrical properties, with low resistivity and high carrier concentration, showing metal-like properties. ITO films also have excellent optical properties, with high transmittance to visible light, high reflectivity to infrared light and high absorption rate to ultraviolet light. In addition, ITO films have high degeneracy, good physical and chemical stability, and good adhesion to the substrate. ITO films have been well applied in the field of flat panel displays such as liquid crystal display and touch screen, and in the field of optoelectronic devices such as light-emitting diodes and solar cells.Compared with nanosecond laser, femtosecond laser processes materials with smaller thermal effects. The ablation efficiency of femtosecond laser with lower laser fluence is lower. Improving the laser fluence of femtosecond laser can effectively improve the processing efficiency, but also reduce the processing quality. Using femtosecond laser pulse train can improve the processing efficiency and ensure good processing quality. After the first pulse interacts with the material, the second pulse interacts with the molten ejecta formed by the first pulse, which can effectively reduce the size of the ejected particles. At present, the mainstream methods of generating pulse train are complicated in principle and equipment, poor in stability, and difficult to change sub-pulse interval, such as Michelson-like interferometer. The pulse train generator based on Fabry-Perot (F-P) cavity is simple, low-cost and flexible in sub-pulse interval variation. In this paper, we use pulse trains generated by F-P cavity to process ITO films with a thickness of 185 nm, and the sub-pulse interval can vary within the range of 1~1 500 ps. High-quality etched lines and complex wires were processed on ITO films.A high-quality etched line needs to have the following characteristics. First, the film is completely etched through. Second, the line width is narrow. Third, the line edge roughness is small. Fourth, the angle between the side wall and the sample surface should be close to 90 degrees. Fifth, the degree of protrusion on the line edge is small. Sixth, the etched volume of bottom glass is small. When comparing the appearance of two etched lines, we also take the above six aspects as evaluation criteria. Firstly, we study the etched lines processed by the original Gaussian light. We constantly change the laser fluence and scanning speed, and explore the change of the evaluation criteria of the etched line under different laser fluence and scanning speed. Secondly, we compare the overall appearance of etched lines processed by pulse train and Gaussian light under various parameters, and find that the edge roughness of etched lines processed by the pulse train is much lower than that processed by Gaussian light, which is also the core innovation point of this paper. Finally, we study the etched lines processed by pulse train. We constantly change the laser fluence and scanning speed, explore the change of the evaluation criteria of etched lines under different sub-pulse intervals, laser fluence and scanning speed, and find a set of optimal parameters for processing etched lines. High-quality etched lines were fabricated when the sub-pulse interval is 150 ps, the laser fluence is 0.49 J/cm², and the scanning speed is 0.2 mm/s. The line width is only 1.45 μm at the top and 0.95 μm at the bottom, and the line edge roughness is only 9.48 nm.After obtaining the optimal parameters for processing etched lines, we explore the influence of the interval between two adjacent etched lines on the appearance of etched lines. We keep changing the distance between two adjacent etched lines and observe the change of the overall appearance of etched lines. According to a large number of experimental results, we believe that when using this particular set of optimal parameters, and when the center distance of two adjacent etched lines is more than 2 μm, the appearance of an etched line is basically not affected by other etched lines, and processing multiple etched lines can be regarded as a simple repetition of processing an etched line. According to the above experiment, we processed complex wires with smooth edges and uniform width of only 2 μm.In summary, the appearance of the etched lines processed by pulse train is better than that processed by Gaussian light, especially the line edge roughness is significantly improved. Femtosecond laser pulse train can take both processing accuracy and processing efficiency into account, suitable for precise processing. Laser pulse shaping is expected to overcome the problems of thermal effect and insufficient energy deposition during femtosecond laser processing, reduce the size of ejected particles and improve the processing efficiency and accuracy.