Abstract: The non pillar sublevel caving method with high efficiency and safety was adopted in Xiagao Iron Mine.In September，2013，the roof hanging phenomenon almost appeared at the same time in the -26 m section and -37 m section containing 5 routes.Besides the poor stability of the ore-body，the main reason for large-scale roof hanging is that the design and construction is not reasonably arranged according to its own situation of mine.The insufficient height of cutting groove，and the less ore-drawing quantity from upper ore-body can not meet the requirements.Some factors such as too much blasting destruction lead to the roof height of ore-body declining，and leave insufficient compensation space for follow-up holes blasting.At the same time，such factors as thick reserved row surface protection layer in design，lower charge density，and no clogging at the top of holes make it difficult to penetrate through the upper covering layer.Blasting produces a large number of bulks，which hides the dangers for the suspension roof.By means of study and practice on the design and construction，the prevention measures are put forward for the present situation of mining，thus providing the technical support so as to avoid from frequent appearance of hanging arch.

Key words: Non-pillar sublevel caving method, Analysis of hanging arch, Preventive measures