Based on the laboratory test, the destruction process of with or no suspended cut-off wall and different soil structure of 3 kinds of embankment piping were simulated, studied the mechanism of suspended cut-off wall control piping development and the impact of suspended cut-off wall on the development process of piping. The test results show that, set of the suspended cut-off wall in double layer and three layer embankment, the suspended cut-off wall can change the distribution of the osmotic pressure inside the gravel layer and the development path of piping failure, improve the hydraulic gradient of piping failure, can reduce the flux, the sand content and the extent of damage when the piping occurred. However, the piping failure forms of double and three layer embankment with the suspended cut-off wall are different, in double layer embankment, on the upstream side of the cut-off wall the piping failure was developed in the internal sand, but in three layer embankment, on the upstream side of the cut-off wall the piping failure was developed on the top surface of the sand layer.