The Q345 plate steel austenite recrystallization behavior and strain accumulation during rolling were investigated through thermal simulation and rolling. The effect of the recrystallization behavior on the microstructure and properties of the steel was discussed and analyzed. The control principles of the pass reduction in the austenite recrystallization region and partial recrystallization region were established. It is found that to increase the thickness of intermediate billet in the finish temperature interval of 880-820 ℃ is favorable to grain refinement.The result has been applied to the industrial production of the 3 500 mm plate mill of Shougang Group. The average grain size of the steel plate conforms to ASTM No. 10-12, and the grade of band structure has been reduced to below 1.5.