In order to explore different low stiffness of pile caps of gravity wharf structure dynamic response rules, the first of a gravity wharf was established based on ABAQUS finite element model refinement, secondly the changing structure of low pile caps on the number of piles, pile diameter and the concrete strength grade, to get different low stiffness of the pile caps, the input three ground motion to the space, to explore the low pile caps of gravity wharf with low seismic response of the pile caps stiffness change rule. The analysis shows that when the stiffness of pile-cap structure changes, the overall horizontal displacement of the structure decreases with the increase of pile diameter, increases with the increase of concrete strength, and increases with the increase of pile number. The peak acceleration increases with pile number and decreases with pile diameter. The dynamic earth pressure at the pile side is much higher than that at the back of the wharf. The dynamic earth pressure at the pile side increases with the increase of pile number, pile diameter and concrete strength grade.