Abstract: Pile foundation is the primary foundation form of high buildings on soft ground.The length of pile foundation is concerned with the anti-seismic ability of unitary structure.While pile foundations are widely used at present,there is little research about the relationship of structure anti-seismic ability and the length of pile foundation.2D dynamic FEM model of high building with pile foundation on soft ground is created with data of one high building with frame structure in Shanghai.Transversely isotropy material is used to simulate the soft ground;spring-dump artificial boundary to semi-infinite ground;film element to the contact and slippage performance of pile and soil;and pile-soil-structure interaction is considered.Seismic monitor data besides one subway station in Shanghai is used as input earthquake wave.Series of dynamic FEM computing is proceeded with different pile length while holding all other parameters.The influence of pile length to the anti-seismic capability of building and pile foundation is analyzed,optimized scheme is advanced.