Abstract: Through single pile static load field tests and finite element analysis, the distribution law of pile side friction in vertically layered foundation was studied. It was found that there is a sudden change in side friction at the soil interface. The pile side friction near the soil interface is about 2-6 times that of a single soil layer, and the sudden change range is 1-2 meters on both sides of the interface. The accumulation of lateral friction stress is mainly on the "hard" soil layer side, and the elastic modulus of the soil on both sides of the soil interface has a certain impact on the accumulation of lateral friction stress. As the difference in elastic modulus of the soil on both sides increases, this influence gradually decreases.