This article makes series of defect analysis by acid washing, planning, metallurgical structure, SEM and energy spectrum analysis in the samples from the plate, which has flaw detection and heavy gauge (≥25mm). It thinks that the mainly reasons of the flaw detection are central segregation layer, inner cracks, inner hydrogen induced cracking and cinder inclusion, at the same time inclusion is usually the origin of cracks. When the heavy gauge plate is produced which has less than 6.0 compression ratio and detection requiring, the production process route should be select after considerations in the steel quality, metallurgical structure quality, slow cool aging (≥48h) and rolling aging (≥24h). At the steel quality, it should be steel gas [H] controlled below 2.0ppm, [S] below 0.010% and total oxygen [O] below 25ppm. And metallurgical structure quality of the slab is mainly decided by the series of process conditions including degree of superheat (15~25℃), cast speed, dynamic secondary cooling system, DSR, liquid level control (±5mm) and equipment work conditions.