The invention relates to a machine tool, a tool assembly and a tool holder of the machine tool. The machine tool comprises a machine tool main body, a main shaft and a supporting unit, and the tool assembly is arranged between the machine tool main body and the supporting unit; and the tool assembly comprises a tool and the tool holder, the tool holder comprises a center shaft, a tool disc is arranged on the center shaft, the tool is mounted on the tool disc, and the two ends of the center shaft are connected with the main shaft and the supporting unit correspondingly; and receding spaces foraccommodating a workpiece when the workpiece and the tool disc conduct relative movement along the axial direction of the center shaft are formed between the tool disc and the main shaft connecting end as well as the tool disc and the supporting connecting end, the machine tool further comprises a worktable, and the worktable and the tool disc can move relatively along the axial direction of the center shaft. When the diameter of a flange is large, the worktable can drive the workpiece and the center shaft to move axially along the axial direction of the center shaft. The workpiece moves between the receding space between the tool disc and the main shaft connecting end as well as the receding space between the tool disc and the supporting connecting end, and the shape required by the end face of the workpiece can be machined at one time without turning the workpiece.