Abstract: A finite element model of Q345B ultra-heavy plate rolling was established and the effect of temperature gradient on the strain in the plate core was investigated during the rolling process. The grain size after austenite recrystallization was calculated and compared with tradition processes. The result of simulation was proved by large specimen plane stain experiment and indicated that the process with temperature gradient is favor of strain increasing in the plate core, and the maximum of increment is 61.35%. The calculation and experiment proclaim that the grain size in the plate core is refined by temperature gradient rolling, moreover, increasing the mechanical properties of the ultra-heavy plate.