Abstract: In response to the challenges of the lack of design basis for the ultrafine tailings filling sys ⁃ tem and the low efficiency of natural sedimentation in the Tianxing Iron Mine，a systematic flocculation sedimentation experimental study was conducted using tailings similar to those from the Sijiaying Iron Mine as substitute samples.Based on particle size analysis and determination of physicochemical properties of the tailings，the appropriate flocculant type，optimal dosage，and key process parameters were determined through static flocculation sedimentation comparison，reagent dosage optimization，and dynamic thickening simulation validation.The results indicate that the tailings are ultrafine，with particles smaller than 38 μm accounting for 45.26%，a median particle size of 44.96 μm，and poor natural sedimentation performance. Static screening tests of five flocculants showed that the anionic flocculant 6920 performed best，with an optimal dosage of 20 g/t.Dynamic thickening tests further determined the optimal unit area processing ca ⁃ pacity to be 0.5 t/（h·m²），under which the underflow concentration reached 70.1%，the solid content of overflow water was 89.2 ppm，and the fluidity was 14.5 cm，meeting the requirements of the filling pro ⁃ cess.The research results achieved synergistic optimization of high underflow concentration and low solid content in overflow water，significantly improving the thickening efficiency of fine tailings while reducing reagent consumption.This provides key parameter support for the design of efficient thickening systems for ultrafine tailings and offers important reference value for similar mine filling processes.

Key words: tailings, static flocculation sedimentation, dynamic flocculation sedimentation