The roof is cemented backfill in underhand drift cut-and-filling stopping, stability of cemented fills is the key to safety of mining. Through numerical simulation test, simply supported beams subjected to uniform was considered mechanical model of backfill roof. and failure modes of backfill roof was found through physical modeling experiment. The results show that the failure of backfill roof is first happening from the center at the bottom of backfill, the final result is that falling arch. Based on the the result of the experiment, finally, The reasonable reinforcement pattern was proposed to avoid failure of backfill roof.