Abstract: A method and construction of growing wafer ingot by having a thermal shield disposed on an opening of a crucible, an opening approximating a polygonal contour disposed on the thermal shield to control gas current, heat conduction and heat radiation in ingot growth, an isotherm of condensation temperature in ingot growth approaching a polygonal form to grow the ingot into a form approximating the preset sectional form of a polygon for minimizing the material to be cut off in the subsequent process of slicing wafer ingot into chips.