Abstract: TMCP process was applied to the rolling of 70 mm-thick Q345C heavy plate steel to control its strength, ductility and toughness. Describes the process and investigates the relationship between the controlled rolling process and the microstructure and properties of the steel as well as the structural morphologies. The results showed that the mechanical properties of the plate specimens thus rolled with heavy reduction in unrecrystallized zone and without heat-treatment can meat the requirements as listed in the Standard GB/T 1591-94, no matter what cooling type is taken (by air or accelerated). The mechanical properties are well homogenized in thickness direction. Accelerated cooling enables the ferritic grains to be clearly finer, but the size of ferritic grains in surface layer and in core are slightly different. The results of investigation will provide a reference for energy saving and cost reducing in the production of 70 mm-thick heavy plates.