Abstract: The recrystallization behavior and accumulative effect of strain of Q345 plate steel were investigated by thermal simulating tests and pilot rolling tests. How the recrystallization affects the microstructure and properties was discussed, thus determining the way to control the pass reduction/deformation in austenite recrystallization region and partial recrystallization region on principle. It was found that increasing the temperature-holding thickness of billet at 880-820°C as the temperature range of finish rolling is favorable to grain refining. The findings have been applied in the 3500 mm Plate Mill Shougang where the average grain size of the plate rolled is up to ASTM Grade 10-12 with the band structure down to below Grade 1.5.