The main objective of adding piles to a raft is sometimes for settlement control. In design, the number of piles for reduce settlements under work load to a tolerable limit is usually small. This often results in a high stress in piles that may impede the application of this foundation due to the limits on raft stress or pile stress in practice. An alternative is to install a cushion between piles and raft. In this paper, the performance of disconnected settlement-reducing piles is studied. Based on some simplifications, a mechanical model of pile penetration into cushion and a calculation method of pile-soil interaction are respectively formulated. In consideration of stress-deformation coordination of pile-soil-cushion, a calculation method of pile-soil stress ratio is presented. Optimization design of disconnected settlement-reducing piles can be performed with this method.