Abstract: Macro-morphology of steel heap sample during HRB400E bar rolling was observed，and morphology and structure of cross section of stacked steel sample were examined by optical microscope. It is considered that，the reason for causing steel heap accident is that the middle crack of billet is exposed at the end，the crack is oxidized on both sides during heating furnace，the head is split during rolling，and the rolling mill cannot bite in normally. Based on the analysis results above，the secondary cooling intensity of continuous casting was improved，the internal quality of slab was improved，and the steel heap accident caused by the internal quality of slab was eliminated.

Key words: HRB400E steel, steel-heaping, intermediate crack, cooling intensity