Abstract: Effect of normalizing and tempering heat treatment processes on the microstructure and mechanical properties of the ton-scale China low activation martensitic (CLAM) steel was analyzed. The results show that the normalizing temperature decides the prior austenite grain size, while the tempering temperature influences the substructures. Compared with the normalizing temperature, tempering temperature has larger effect on the mechanical properties of ton-scale CLAM steel. The optimum microstructure and mechanical properties could be achieved for the ton-scale CLAM steel under the heat treatment processes which consists of 980 ℃ normalizing and 760 ℃ tempering.