To make full use of the advantages of soft mattress and twisted double “H” permeable frame for bottom protection,and reduce the project investment,we study the hydrodynamic characteristics,the protective effect and applicable parts and arrangement of the submerged breakwater downstream’s soft mattress and twisted double “H” permeable frame joint bottom protection by the generalized flume test.The results show that sinking current appears near the dam base and transverse circulation emerges behind the dam;The framework group can effectively slow down the level surface water flow to the beach,but it is unable to reduce the vertical flow of overflow the dike.The framework can not be directly thrown into the base of the dike or the base of the dam,so the framework should be thrown into the soft mattress of bottom edge.A side frame thrown width of about 20 m (5 m overlapping) is advised,and the framework thrown density of 2 sets m2 is the best.The results can provide technical reference for the engineering design.