The long-short-piles composite foundation technology can improve the bearing capacity of the foundation and reduce the settlement.This technology has good economy and security,which has good prospects for development.According to the characteristics and the research situation of the technology,this paper discusses the main factors (the thickness of cushion,the length and replacement ratio of long piles,the length and replacement ratio of short piles,the upper structure stiffness) affecting the settlement and the load sharing ratio,and draws some useful conclusions.Cushion does not affect the differential settlement of raft,and the average settlement increase,slightly with the thickness of cushion.But there is certain limit.When the thickness of cushion is in a certain range,the load sharing ratio of long pile decreases significantly with the increase of the thickness of cushion layer,the soil mass increases significantly,and the load sharing ratio of short pile increases.If the thickness of the cushion continues to increase,the load sharing ratio tends to be stable.The influence of the length of long piles which are on the differential settlement of raft bottom is limited.But the increase is slow and the average settlement decreases.The load sharing ratio of long piles increases with the length of the long piles.But the soil mass and the short piles decrease in a certain limit.When the replacement ratio of long piles exceeds a certain range,the influence on the settlement of raft bottom and the load sharing ratio of pile-soil is not obvious.The length of short piles and replacement ratio of short piles have little influence on the settlement of raft bottom and the load sharing ratio of pile-soil.The structure stiffness has little influence on the differential settlement of the raft bottom and the load sharing ratio of pile-soil.The average settlement of the raft bottom increases with the structure stiffness,but then it increases slowly.This conclusions can provide a reference for the design and application of the long-short-piles composite foundation.