Abstract: The process of deposition and consolidation of fragmented multiphase materials is the basis and prerequisite for studying their strength and deformation. To find out the evolution laws of stress and pore water pressure during the deposition of fine iron tailings and reveal the strength formation mechanism and deformation characteristics of tailings reservoir, the sedimentary slope of tailings, stress, pore water pressure and effective stress during the deposition process are monitored by field large-scale flume tests. Meanwhile, the shear strength of tailings after deposition is determined by the vane shear apparatus. On this basis, grain-size distribution and permeability characteristics of tailings from different sedimentary sections are tested to analyze the evolution mechanism of tailings sedimentation rate. The experimental results show that the accumulation form and permeability characteristics of tailings with extremely uniform particle grinding are different from those of soils. Due to the large proportion of tailings particles and uniform distribution of particles, increasing the permeable boundary of tailings can improve the formation rate of effective stress of tailings better than applying external loads. The surface hardening of tailings and the sealing of micro-pore trigger the formation of effective stress in tailings. It is difficult to infiltrate the stagnant water in the upper layer. Necessary diversion measures should be adopted to reduce the influences of high potential fluid on the stability of dam construction.