Abstract: To study the vertical vibration characteristics of single and group friction piles in multi-layered soil, a series of field vertical pile foundation dynamic tests are carried out, a vertical calculation model of friction single pile and pile group in multi-layer soils is established and a theoretical calculation method of dynamic response of a single pile and pile groups is obtained. The displacement vibration curves, pile head displacement amplitudes, acceleration vibration curves, dynamic stiffness and group pile efficiency coefficients of a single pile and group piles under vertical dynamic loads are obtained through on-site experiments. The interaction laws of group piles during vibration are also analyzed. The correctness of the experimental results is verified by comparing the dynamic stiffness of pile head and dynamic efficiency coefficient of pile groups obtained from the experiment with the theoretical calculation method. The variation law of displacement vibration curve, acceleration vibration curve, dynamic stiffness of pile head and dynamic efficiency coefficient of pile groups are analyzed through experimental results. The study shows that there are interactions between piles during the vibration process of pile groups, resulting in a non-multiple relationship between dynamic stiffness of pile head of pile groups and a single pile; The interaction between piles weakens as the distance between piles increases and number of piles decreases.