Abstract: An iron tailing in Shaanxi is difficult to settle，the tail water quality is poor， and the tail water has not been reused for a long time.This not only wastes water resources， but also has environmental pollution problems. In order to accelerate the settlement of tailings and improve the quality of tail water to promote the reuse of tail water，different kinds of inorganic and organic flocculants were selected to study the sedimentation of tailings slurry.The interaction of FeCl3 and new organic flocculant of AL9020 on flocculation sedimentation of tailings was also investigated.The results showed that the fine grain size of the iron tailings makes it difficult to settle naturally. When the inorganic flocculant is used alone， the sedimentation speed of the tailings is slow，but the turbidity of the clarification water is low.And when the organic flocculant is used alone， the sedimentation speed of the tailings is fast，but the turbidity of the clarification water is poor. The combination of FeCl3 and AL9020 flocculants can improve the settling speed of tailings and reduce the turbidity of clarification water，which can enhance the settlement effect of tailings.Under the optimal medicament system with the FeCl3 and AL9020 dosage of 200 g/m3 and 15 g/m3 respectively， the settling velocity of iron tailings is 301.68 m per day，and the turbidity of clarification water is 23NTU. The acceleration of the sedimentation rate and the decrease of the turbidity of the clarification water provide quality assurance for the reuse of tail water. And the combination of inorganic and organic flocculants produces a synergistic effect， which can significantly improve the settlement effect of tailings and provide a reference for the settlement of tailings， especially fine-grained tailings.

Key words: iron tailing, fine grain, combination of the flocculants, settling velocity, turbidity