The second stage cofferdam was formed by filling weathered rock soil under 60 m deep in water in the main riverbed. To make the materials more close,large power vibrators were used to compact the filling material. In order to detect the vibro-compaction effects on filling rock soil,in-siteand lab tests were conducted to investigate its physical and dynamic properties The results show that all parameters indexes of the cofferdam can satisfy the design demand and its reinforcement effect is well