In the fields of the working shaft at the east bank of Zhuhai Tunnel and the foundation pit of the excavated section at the west side of the Guadingjiao Mountain, the upper part is mainly silt layer, and the lower part is mainly moderately weathered and slightly weathered granite layer. The bedrock has high strength and large fluctuation of rock stratum. The diaphragm wall is used for supporting the foundation pit. But it is difficult to form groove in its construction process. In order to ensure the construction progress and grooving quality of diaphragm wall, the different mechanical equipment combinations are adopted for the comparison. Finally, the mechanical combination of "rotary excavating drill + double-wheel mill" is selected suitable for grooving diaphragm wall in soft soil - granite stratum. The practice results show that the selected grooving construction technology can effectively improve the construction efficiency and grooving quality of diaphragm wall.