The invention belongs to the technical field of fasteners and discloses a planet carrier and main shaft locking structure. The planet carrier and main shaft locking structure comprises a connecting flange, a locking disc and a fastening device. The connecting flange is arranged on a planet carrier and extends in the axial direction of the planet carrier, the inner circumferential face of the connecting flange is arranged outside the main shaft in a sleeving manner, and at least part of the outer circumferential face of the connecting flange forms a first conical face in the axial direction. The locking disc is arranged on the outer circumferential face of the connecting flange, and the inner wall of the locking disc is provided with a second conical face matched with the first conical face. The fastening device is used for fixing the locking disc to the planet carrier in the direction opposite to the axial direction. By means of the planet carrier and main shaft locking structure, thesecond conical face of the inner wall of the locking disc is matched with the first conical face on the outer circumferential face of the connecting flange, then the fastening device is used for locking the locking disc on the planet carrier in the axial direction of the planet carrier, main shaft locking can be achieved, the structure is simple, and the locking attaching force is high.