In solar-grade single crystal silicon Cz growth, the geometries of argon flow guide, heat shields and insulations are main parameters affecting the heat exchange and crystal growth conditions. By changing the above parameters, an optimization of crystal growth was attempted. Numerical simulations before and after optimization were Provided to verify the results. Through analyses of the temperature distribution in the crystal and melt. the argon gas flow between the radiation shield and the quartz crucible, and the thermal stresses in the crystal, it was found that the optimized heat shield can reduce the baking of crystal by the heater; the optimized side insulation can prevent the heat loss upward, and the optimized flow guide can decrease the SiO deposition on the upper wall. After optimization, under the same heater power, the crystallization rate is increased over 35%, without increase in macro-dislocation probability; the optimized V/G ratios along crystal radius are greater than the critical value, thus the probability of occurrence of OSF-ring in the crystal is also reduced. (C) 2009 Elsevier B.V. All rights reserved