According to effect plinciple of surface-active agent experiment study on strength and fluidith of two cemented fills with unclassified tailings in which was added a different active agent was performed using physicochemical methods. The equation of uniaxial compressive strength of cubic specimen of filling material with surface-active agent for 7,14 and 28 days age was derived from triple factors quintic level quadratic regression orthogonal design in the experiment process. The experiment results indicated that strengthening effect of ,1 surface-active agent is dependent on its type and dosage as well as on cementsand ratio of cemented fill,but to a less extent on the concentration of filling material. Collapsibility test shown that surface-active agent is able to improve fluidity of unclassified tailing fill material greatly, thus to increase fill line.