Cutter is the main cutting tool, arranged on both sides of the cutter opening slot, the cutting principle is the shield machine forward at the same time, the cutter with the cutter rotation on the excavation surface of the soil to produce axial (along the tunnel forward direction) shear force and radial (cutter rotation tangent direction) cutting force,in the cutter rotation, the cutter blade and cutter head partially inserted into the ground within the soil, and constantly cutting down the soil in front of the excavation.In the hard rock stratum under the cutter mainly plays the role of scraping slag,not directlyinvolvedin cutting.