This paper adopts sedimentation experiment to study the sedimentation process of one molybdenum ore flotation tailings and to investigate the effects of lime and sodium silicate on sedimentation performance of tailings. Through the experiment on sedimentation speed and compressive layer density, it reveals the sedimentation performance rules of these tailings. Meanwhile, it explores the effects of lime and sodium silicate on sedimentation dry beach of tailings. The research shows that: lime could effectively ameliorate the non-easy sedimentation caused by sodium silicate; when the dosage of sodium silicate is 300～800g/t, the sedimentation performance can reach the best reasonable pH value 9-10. Besides, the study also indicates that both sodium silicate and lime are unfavorable to form sedimentation dry beach by tailings of concentrating mill.