The mechanical behavior and mechanism of the interface between structure and coarse grained soil are investigated through simple shear tests on the conditions of bentonite slurry, clay slurry and without slurry, respectively. The results indicate that different kinds of slurry have important influence on shear strength. Compared with the interface without slurry, the shear strength with bentonite slurry reduces by 45% approximately, significantly more than clay slurry which reduces by 10%. The value of the friction angle with bentonite slurry is about 60% of that with clay slurry. Shear displacement increases as upright stress increases when reaches its failure states at the same height, and shear displacement with bentonite slurry is smaller than that with clay slurry when with the same upright stress and height. The upright displacement with bentonite slurry is greater than that with clay slurry under the same upright stress. In addition, shear dilatation is apparent under the low normal stress when without slurry. Otherwise, it appears as shear contraction.