A method for manufacturing a monocrystalline silicon with a Czochralski process, comprising: providing a polycrystalline silicon and a dopant to a quartz crucible; placing the quartz crucible in a single crystal furnace and vacuumizing the furnace, and melting the polycrystalline silicon under an atmosphere of a protective gas to obtain silicon melt; after a temperature of the silicon melt is stable, immersing a seed crystal into the silicon melt to start a seeding process, during the seeding process, lifting a water-cooling heat shield in a direction away from a surface of the silicon melt to adjust a distance between a bottom of the water-cooling heat shield and the surface of the silicon melt to a first preset distance; after the seeding process is completed, performing a shouldering process to continuously pull the crystal, and gradually increase a diameter of the pulled crystal to a preset width; starting a constant-diameter body growth process, lowering the water-cooling heat shield in a direction towards the surface of the silicon melt to adjust the distance between the bottom of the water-cooling heat shield and the surface of the silicon melt to a second preset distance; after the constant-diameter body growth process is completed, entering a tailing stage during which the diameter of the pulled crystal is gradually reduced until the pulled crystal is separated from the silicon melt; and cooling the pulled crystal to room temperature and taking out the cooled crystal from the single crystal furnace as the monocrystalline silicon, characterised in that during said performing the shouldering process to continuously pulling the crystal, a first pulling speed of the crystal is in a range from 50mm/h to 80mm/h, so that the diameter of the crystal is gradually increased to 230mm-310mm. providing a polycrystalline silicon and a dopant to a quartz crucible; placing the quartz crucible in a single crystal furnace and vacuumizing the furnace, and melting the polycrystalline silicon under an atmosphere of a protective gas to obtain silicon melt; after a temperature of the silicon melt is stable, immersing a seed crystal into the silicon melt to start a seeding process, during the seeding process, lifting a water-cooling heat shield in a direction away from a surface of the silicon melt to adjust a distance between a bottom of the water-cooling heat shield and the surface of the silicon melt to a first preset distance; after the seeding process is completed, performing a shouldering process to continuously pull the crystal, and gradually increase a diameter of the pulled crystal to a preset width; starting a constant-diameter body growth process, lowering the water-cooling heat shield in a direction towards the surface of the silicon melt to adjust the distance between the bottom of the water-cooling heat shield and the surface of the silicon melt to a second preset distance; after the constant-diameter body growth process is completed, entering a tailing stage during which the diameter of the pulled crystal is gradually reduced until the pulled crystal is separated from the silicon melt; and cooling the pulled crystal to room temperature and taking out the cooled crystal from the single crystal furnace as the monocrystalline silicon, characterised in that during said performing the shouldering process to continuously pulling the crystal, a first pulling speed of the crystal is in a range from 50mm/h to 80mm/h, so that the diameter of the crystal is gradually increased to 230mm-310mm.