[Objective] In order to prevent the seepage problems in reservoir and cofferdams in lots of overhead structures, the paper try to use a new controllable clay composite paste in strata with following water. [Methods] An experiment was designed to study the effect of a new type of compound paste with a new admixture, which has low fluidity, controllable condensing time, good water resistance and water release, on the anti-leakage and sealing process in the soil strata with flowing water. [Results] The content of curing agent and quick condensing agent in the paste has a significant effect on its resistance to water flow, the initial condensing time and the flow rate. Adjusting the content of curing agent and quick condensing agent could effectively change the physical and mechanical properties of the composite paste, thus meet the engineering requirements. [Conclusion] This kind of controllable clay can be used to deal with the leakage problems in the dynamic water stratum with strong permeable sandy pebbles and effectively improve the seepage-proofing ability of the reservoir.