Abstract: Previous studies have shown that high bittern composition has negative influence on strength of cemented tailings backfilling block.But sometimes in order to improve the early strength of cemented filling block，few early strength agents，such as sodium sulfate，sodium chloride would be added.In order to study the effect of bittern on the strength of cemented tailing backfilling block in Sanshandao Gold Mine，the strength of cemented tailings test block and cement test block respectively mixing with bittern and tap water have been researched.And XRD technology is used to analyze the cement test block mixing with bittern and tap water.The results show that the bittern in Sanshandao Gold Mine improved the early strength of cemented tailings test block and cement test block.The main reason for the difference is that the mixing water has different components，making the hydration reaction different in internal test block.Cement test block mixing with bitter generated more portlandite and C-S-H gel.Although the amount of ettringite which is harm for the specimen strength increased，in terms of early strength，the positive effect of C-S-H gel and portlandite is more obvious.The long-term strength of cemented tailings backfill affected by bittern will be experimented.

Key words: Bittern, Cemented backfilling, Cemented tailing test block, Hydration reaction, Uniaxial compressive strength