Abstract: For two automobile sheet materials with different strength levels and thicknesses, fatigue specimens with different test section widths, different parallel lengths and different arc radius were designed. Without the use of anti-buckling device, high cycle fatigue tests with stress ratio R=-1 at different stress levels were carried out, and the shape and size of the fatigue specimens of automobile sheet materials were determined by the number of fatigue life cycles of specimens with different sizes under the same stress cycle form. The results show that for automobile sheet with thickness of 0. 8~3 mm, the uniform-gage fatigue specimen was more suitable for the tensile-compressive high cycle fatigue test than the hour-glass fatigue specimen. The recommended sizes of the uniform-gage fatigue specimens (a is the thickness of the specimen) were test section width b=(1-3)a, parallel length L_c=(1-3) b, and arc radius r=(3-10) a.