Abstract: Star cracks often appear on the surface of steel plate produced by a steel plant, the reasons of such cracks were analyzed by means of macroscopic observation, metallographic examination, scanning electron microscopy analysis and energy spectrum analysis. It was concluded that the main reasons of star cracks on the surface of steel plate were the existence of bubbles and intergranular cracks on the surface of slab, or the selective oxidation or high content of low melting point substances in slab. Finally, the corresponding improvement measures were put forward.