Photovoltaic power generation has been widely adopted for its advantages such as green, renewable, high energy quality and not restricted by the geographical distribution of resources. Monocrystalline silicon has gradually surpassed the market share of polycrystalline silicon photovoltaic cells with the advantages of low attenuation rate and high conversion efficiency. However, cost issues and productivity issues have been restricting the development of the monocrystalline silicon solar industry. This paper proposes a thermal shield structure of a Czochralski single crystal furnace that drops with the drop of silicon liquid level during crystal growth. To solve the problems of lower crystal pulling speed and stability, as well as the increase of crystal pulling energy consumption caused by the rise of the crucible during the crystal pulling process, taking the CL120-97 single crystal furnace thermal field as the research object, the finite element simulation was used to analyze the flow field of argon gas and the thermal field of the crystal and melt before and after the optimization of the single crystal furnace. The analysis and simulation results show that the optimized single crystal furnace can not only improve the pulling speed and quality of the single crystal, but also effectively reduce the energy consumption of the single crystal furnace.