Abstract: The cover of the open pit to underground natural phenomena on the use classification of the mine caving mining ventilation，temperature，dilution and other indicators of ore loss have a more significant impact，but when the coating in the filling to form a reasonable natural grading，domestic research is still in the blank stage.The background for the study of Shougang Xingshan iron mine，using theoretical analysis，physical simulation，field trials and other research tools，the coverage of the open pit to underground layer of backfill laws of the natural classification system for in-depth analysis of the results come Xingshan iron mine waste rock dump using artificial backfill to form a reasonable hierarchical structure and thickness of the natural cover is feasible.

Key words: Open pit to underground, Covered rock, Backfill, Natural classification