Abstract: Due to the fine particles and large specific surface area，the high concentration ultra-fine tailings paste generally has problems such as high viscosity，poor fluidity and difficult pumping. In order to improve its pipeline transportation performance，the ultra-fine tailings of Fankou Lead-Zinc Mine were used as raw materials，and conch cement and new rock-solid materials were used as cementitious materi⁃ als. The yield stress of paste with different plasticizer contents was tested by RST-SST paddle rheometer system. The results show that the effect of plasticizer on yield stress is significantly dependent on the type of cementitious material. In the solid rock system，the yield stress continues to decrease with the increase of the content，and there is no risk of over-doping；in the conch cement system，the yield stress decreases to the lowest when the dosage is 1.5‰，and increases to 2‰ after the yield stress increases，and there is an obvious optimal dosage window. Based on this，the suggestion of differential ratio is put forward. The recommended dosage of plasticizer in the solid rock system is 2‰，and the conch system should be con⁃ trolled at 1.5‰. The research results can provide accurate and economical admixture application scheme for high concentration ultrafine tailings filling project.

Key words: ultra-fine tailings, plasticizer, yield stress