In slope engineering, the foundation grooves of slope protection gird beams are mostly excavated manually. However, manual excavation presents problems, such as low construction efficiency, uneven groove bottoms, inconsistent cross-section groove widths, and curved groove axis, which reduces the quality of cast-in-place grid beams or complicates the installation of prefabricated grid beams. To address these issues, a mechanized grooving device for slope protection grid beams has been developed and successfully applied in the project. The grooving device is composed of interlocking dual spiral cutter heads, a mechanism for the groove width and depth adjustment, a cutter head working platform, a platform azimuth adjuster, a cutter head sliding mechanism, a hydraulic motor, a hydraulic power system and a platform anchoring mechanism. It can be used to groove on soil and strongly weathered rock slopes at different slope angles, and the foundation grooves of slope protection gird beams of different depths and widths can be carved according to the design requirements. Moreover, the grooved trenches feature flat bottoms, consistent widths, and straight axis, making it easy to install prefabricated grid beams and greatly improving the quality of cast-in-place grid beams. According to the construction statistics of a slope project in Guangdong, the grooving speeds of the grooving device on the slope of soil and strongly weathered rock are about 1.5m/min and 0.5m/min respectively, which greatly improves the construction efficiency and quality.