In this paper, the unconfined uniaxial compression tests on backfills with different cement - tailings ratio in the special large -sized stope in Anqing copper mine are presented. According to the obtained uniaxial compression toughness parameters, the toughness properties are known. The variety of the properties of toughness indexes and the laws are analyzed. It is argued that the most realistic requirement for keeping the integrity of backfill is to assure the backfill with high residual intensity.