Abstract: Objectives Distortion due to flame cutting of thin plate with high tensile strength steel, will directly influence the efficiency and accuracy of subsequent procedure such as assemble and welding during fabrication of ship panel; it is required to examine the generation mechanism and support correction techniques. Methods Taking Q550 plate with thickness of 3mm as research object, out-of-plane buckling and in-plane bending distortion of examined cutting specimen were observed by means of flame cutting experiment and dimension measurement. By thermal elastic plastic FE computation with large deformation, buckling behavior during flame cutting of Q550 thin plate was presented, both distortion tendency and magnitude of predicted results have good agreement with measured data. In addition, heating the region away from flame cutting can reduce buckling distortion about 90% and in-plane bending distortion by 40%. Results Based on generation mechanism of cutting distortion, assisted flame heating with different processing was proposed and applied to improve the cutting accuracy with flame. Conclusions Assisted flame heating with residual plastic strain and inverse bending moment, can effectively reduce the in-plane bending distortion of thin plate; assisted flame heating without residual plastic strain and reduction of mechanical constraint supported by base metal on cutting area, can generate less longitudinal shrinkage force to effectively avoid out-of-plane buckling and partially reduce in-plane bending distortion of thin plate with flame cutting.