Abstract: The first part of the second phase of Tibet Jiama polymetallic copper ore deposit is explored by filling mining method.Because of the filling slurry′s segregation and other reasons in the filling process，the in-situ filling body appears non-uniform，and its strength also has the much difference with standard backfill block in laboratory.The regularity of strength distribution of the filling body in stope was studied by building a large scale three-dimensional similarity simulation experiment system.The results showed that in horizontal direction，the strength of the filling body increased and then decreased with the slurry flow direction.The filling body strength with high cement-sand ratio changed less，and the strength of the filling body near the feed outlet was equal to the strength of standard filling body.In vertical direction，the strength of the filling body increased with its depth，and the filling body strength with high cement-sand ratio increased greatly.The microstructure of the filling body samples observed by scanning electron microscope can essentially explain the reason for the difference in the strength of the filling body.

Key words: Strength of filling body, Regularity of distribution, Characteristic of flow, Microstructure