To study the dynamic response law of large diameter variable cross-section single pile in liquefaction sites under different ground motion intensities， shaking table tests were conducted. Employing the 5010 wave and subjecting the system to ground motion strengths ranging from 0.10g to 0.45g， this study examined the evolution of sand pore pressure ratio， horizontal displacement at the top of the piles， bending moment along the pile body， as well as the time history response of pile acceleration and foundation damage. The test results show that the pore pressure ratio of saturated sand increases obviously with the increase of ground motion strength. The pore pressure ratio of saturated sand increases obviously with the increase of ground motion intensity. When the ground motion intensity is ≥0.30g， the stable value of the pore pressure ratio of saturated sand is near 0.9， and the sand is completely liquefied. Under the action of 0.45g ground motion， the acceleration of pile body， the horizontal displacement of pile top and the bending moment of pile body all reach the maximum. The peak acceleration at different positions along the pile body lags behind that of the input seismic wave， and the acceleration response of the pile top and variable cross-section is weaker than that of the pile tip. The maximum bending moment of the pile appears at the boundary between the liquefied soil layer and the non-liquefied soil layer， and the bending moment at variable cross-section is smaller than that at the soil layer interface. When the ground motion strength reaches 0.30g， the damage of a large diameter variable cross-section single pile occurs. Therefore， in the seismic design of the single pile foundation of a large diameter variable cross-section bridge under a liquefaction site， the bending capacity at the boundary of the saturated sand layer and variable section should be considered to ensure that the strength of the single pile meets the anti-seismic requirements.