Abstract: To control the surface movement caused by mining，the backfill mining method was adopted for underground mining in Sijiaying Changyu iron mine.On the basis of safety production，selecting appropriate parameters of ore block structure is particularly important for the design and construction of the mine.Through the application of FLAC3D to simulating different sizes of ore block structures，the block structure optimal parameters of filling mining method were obtained，which provided the basis to the design and development of mine.

Key words: Mining with backfill, Ore block structure, Optimization