The invention provides a chuck expansion type metal hard tube rotary cutting machine. The rotary cutting machine comprises a supporting device, a sleeve device, a cutting device and at least four expansion devices, wherein a plurality of expansion devices are sequentially connected and arranged on the same axis through connecting frames, two expansion devices located at two ends are connected withthe supporting device, every two adjacent expansion devices are connected by sleeve pipes of the sleeve device in a sleeving mode, and the cutting device is arranged between two adjacent expansion devices. The expansion devices can expand from the inside of the metal hard tube to achieve the purpose of fixing the metal hard tube, and all lengths of the metal hard tube can be fixed, so that an existing equipment which can only clamp and fix the cut part is replaced, the clamping force is more uniform, and the clamping deformation is prevented; the expansion devices can drive the metal hard tube to rotate together, and then the cutting wall thickness distance can be achieved through feeding movement of a cutting knife, so that the cutting task can be completed, a cutting mode that an existing cutting grinding wheel pieces enter the inner part of the metal hard tube is replaced, and the situation that a cut surface is burned and worn is avoided.