To control the settlement and differential settlement of the tube tunnel foundation control under the geologic condition of open sea,deep water and thick & soft base for the Hong Kong-Zhuhai-Macau bridge tunnel engineering immersed tube tunnel,we carry out a comparison between the traditional pile foundation and the composite foundation,and propose the composite bed foundation scheme,which turns from the composite foundation of the PHC rigid pile,high jet grouting flexible pile,and sand compaction piles gradually to the natural foundation and composite foundation bed.The composite foundation settlement calculation analysis and observation data prove the remarkable effect of the composite foundation and composite foundation bed scheme for the control of the settlement and differential settlement.The composition of the tube tunnel’s foundation settlement and the recommended calculation method for the composite foundation are also given,which may serve as reference for similar projects.