Regarding the influence of the arrangement of gravel pile composite foundation on the whole stability of bank slope，numerical modeling analysis and field test are carried out. Using the method of Geostudio finite element software combined with the slope engineering example of a gravel pile composite foundation for simulation calculation，the influence of different gravel pile spacing，driving range and periodic tidal level changes on the stability of the bank slope is analyzed. Meanwhile，the comparative monitoring of the test section of adding gravel pile at the sea front is carried out. The results show that the variation of gravel pile spacing has little influence on the stability of bank slope，the floating range of safety coefficient on the sea side is larger than that on the land side under periodic tidal level variation，and increasing the range of gravel pile in front of bank slope is conducive to the overall stability of bank protection. Under the condition of not changing the pile diameter and pile spacing，widening the scope of gravel pile on the front of the seaside bank slope can enhance the overall shear strength ratio of composite foundation in the sliding surface，and achieve the effect of improving the stability of the bank slope.