Cement mixing pile is one of the effective methods to reinforce soft soil foundation,and the composite foundation is formed by cement mixing pile,soil between piles and mattress bedding layer,which greatly improves the bearing capacity of the foundation and effectively controls the settlement deformation of the foundation.Through taking a soft soil roadbed as the research background,the study analyzes the bearing characteristic of cement mixing pile,and researches influencing factors of composite foundation settlement deformation with numerical simulation,so as to provide reference for projects related to soft soil foundation treatment.