Objective To analyze the influence regularities of different sizes on thermal stress field of bipolar high-frequency electric knife. Methods Based on the ANSYS software, the electric-thermal coupling simulation analysis was performed for thermal stress field of bipolar high-frequency electric knife during working. The effects of 3 different insulation layer thicknesses (0-5, 1-0, 1-5 mm), electrode thicknesses (0-5, 1-0, 1-5 mm) and coating thicknesses (3, 6, 9 μm) on thermal stress field of bipolar high-frequency electric knife were studied. Results If thickness of the insulation layer was larger, deformation of the myocardial tissues would be smaller due to thermal stress, that is, the thickness of the insulation layer was inversely proportional to thermal deformation of the myocardial tissue during working process of the high-frequency electric knife. For the 3 electrode thicknesses, 1-0 mm was a better choice. And for the 3 coating thicknesses, 6 μm was a better choice. Conclusions The component sizes for the high-frequency electric knife have an important influence on thermal stress field, and the result can provide guidance for design of the high-frequency electric knife.