Liquid crystal polymer (LCP) has gained attention in 5G packaging because of its excellent performance as a substrate material in microwave/millimeter-wave circuits. In this study, ultraviolet nanosecond laser was used to conduct the film removal experiment on LCP flexible copper plate. At the repetition frequency of 200 kHz, the effect of different scanning layers, scanning speed, and average power on the film removal depth of LCP material was studied using the control-variable method. To reduce the effect of heat on electronic devices and flexible circuit boards, the variation law of heat-influence zone at the frame of LCP substrate with laser parameters was analyzed based on the LCP characteristics and actual processing results. The experimental results show that when the scanning layer number is five, the scanning speed is 600 mm/s, and the average power of excitation light is 2.1 W, the machining depth can reach 49.84 µm, the uniformity is good, and the heat affected zone at the frame is small, reaching 28.43 µm. The experimental results may provide a theoretical basis for LCP substrate in flexible circuit packaging.