The Ag–Cr film on the LiNbO3 substrate was etched by an ultrafast pulsed laser with a wavelength of 1064 nm, a pulse width of 10 ps, and a repeat frequency of 100 kHz. The effects of laser energy density and scanning speed on the quality of etched grooves on Ag–Cr films were studied to improve the groove quality. The results show that the laser energy density of 5.38 J/cm² and the scanning speed of 500 mm/s are the optimal laser parameters for etching grooves. In this case, the substrate at the bottom of the trench is intact, and there is no obvious crack at the edge of the trench, which ensures that the final etched interdigital electrode has excellent performance. At the same time, the corresponding groove width is about 14 μm, which makes it possible to process high-quality interdigital electrodes with a line width of 14 μm and above, which can meet the needs of interdigital electrodes for surface acoustic wave devices in the biomedical field. A pair of interdigital electrodes for surface acoustic wave devices in the biomedical field were designed and fabricated with optimized parameters. They have high machining accuracy, good surface morphology and no defects such as adhesion between electrodes.