Abstract: Addressing the problem of low impact toughness as identified in the manufacture of the 12Cr1MoVG heavy wall steel tube, the heat treatment process therefore is optimized and, then performed. It is identified that the key measure to improve the tube’s impact toughness is properly controlling the normalization cooling velocity, and accordingly the normalization heat treatment process of “water-cooling + air-cooling” is designed. Relevant operation practice of the said process has proved that desired metallographic structure and satisfactory overall performance of the 12Cr1MoVG tube is obtained.