Abstract: The 2-pass and 10-pass constrained groove pressing deformation were conducted on Q235 steel, respectively, and then the steel was annealed at different temperatures; the thermal stability of the groove pressed steel was studied. The results show that after annealing under 500℃, the microstructures of 2-pass and 10-pass groove pressed specimens were in the recovery stage. The grains were still uniform and fine equiaxed grains, similar to those before annealing. After annealing at 500-680℃, the recrystallization occurred in the specimens and the grains grew with the increase of annealing temperature. After annealing at 680℃, the microstructure of 10-pass groove pressed specimen was more uniform than that of 2-pass groove pressed specimen. With the increase of annealing temperature, the hardness of the 2-pass and 10-pass groove pressed specimens both decreased and the hardness decrease rate of 10-pass groove pressed specimen was relatively large after annealing at 250-600℃. However, the hardness was slightly higher than that of 2-pass groove pressed specimen after annealing at 680℃.