Aiming at fabrication of complex microstructures and micro-patterns, a kind of femtosecond laser micromachining technology based on the BMP image edge tracing was proposed. We introduced the general principle of this technology and discussed the implementation of the machining paths extraction, optimization, tracing and the feedback of the machining procession in detail. On the basis of this technology, control software for femtosecond laser micromachining was developed. Furthermore, we have accomplished the fabrication of complicated two-dimensional (2D) micro-patterns on a copper thin film. The results indicate that this technology can be used for digital control micromachining of complex patterns or microstructures at micron and submicron scales by femtosecond laser. femtosecond laser, image edge detection, micromachining, micro-pattern Citation: Zhang D S, Chen F, Liu H W, et al. Research on the technology of femtosecond laser micromachining based on image edge tracing.Femtosecond laser micromachining is a new type of micromanufacturing technology with many incomparable unique advantages. Firstly, femtosecond laser pulse duration is so short (10 −15 s) that it enables us to obtain extremely high peak power at relative low pulse energy and thereby greatly reduces the energy required for fabrication. For example, when a 10 fs laser pulse at 0.3 mJ pulse energy focuses on a micro-region with diameter of 2 μm, the peak power in the focal spot would reach 10 18 W/cm 2 . Secondly, the energy of femtosecond laser is concentrated in the range of the skin depth, resulting in minimal heat affected zone. And there will be no trace of melting and re-solidification left after the ablation process, accordingly reducing or even eliminating many negative influences caused by the thermal effect in traditional processing. Thirdly, the nonlinear absorption of femtosecond laser can make laser focus into any position inside transparent bulk materials, thus three-dimensional (3D) microfabrication can be realized. In addition, because of the accurate laser ablation threshold for each material, laser energy can be controlled to equal to or slightly higher than the ablation threshold so as to carry on sub-micron fabrication beyond the diffraction limit. With enough short pulse duration and enough high peak power, the femtosecond laser can carry on 2D and 3D fine processing, repair and modification of various materials, especially for high hardness, high melting point, corrosion resistant and brittle materials (such as metals, glasses, ceramics etc.). At present, domestic and foreign scholars have already carried out extensive researchs on femtosecond laser micro-machining in the fields of fabrication of micro-optics, microelectronics, micro-mechanical devices and biochemical analysis system, and the fabricated microdevices including waveguides [1-3], gratings [4,5], micro-electrode [6], Mach-Zehnder interferometer (MZI) [7], and other simple micro-patterns. Moreover, the fabrications of optical switch [8], 3D optical circuit [9,10], ...