Many laser thermal stress forming experiments of high strength steel plate used automobile are done by CO2 laser and the material relevant microstructures are analyzed. Based on the deep study of the changing law on the specimen bending angle, the process parameters are reasonably optimized about laser thermal stress forming. Namely the effect of thermal stress forming is the best when the laser power is 1.5 kW, scanning times are 6, the scanning speed is 1.5m/min and the diameter of laser spot is 3.5 mm and the surface energy changes between 20~45 J/mm2. The conditions are proposed to avoid the ablation phenomenon on the work piece surface. The test results show that the bending angle tends to the direct proportion relationship with laser scanning times, scanning velocity and material width in the effective range of the test parameters. That is a linear relationship when the spot diameter is the less or the more. The effect of the laser power is nonlinear obviously, but the bending angle tends to the direct proportion relationship with the laser power when the laser power is less. The microcosmic grain is smaller near the material surface and the carbide precipitation is less farther the surface.