The relationship between pile numbers and settlement is the most important reference for pile foundation design, based on the deformation control (or design of reducing settlement pile foundation), which is affected by several factors, such as the loading magnitude,the pile arrangement and the soil type. Combined with the measured data from case history, the approximate numerical method and plane strain finite element method are put forward to analyze two piled raft foundations with different pile numbers for multi-storey residential buildings. The effects of different pile spacings on compressive deformation, internal force of foundation and stress-strain distribution of soils are studied, and a reasonable explanation is given for the problem that foundation settlement is almost unchanged after the pile number is reduced by half. The results show that, the lower the loading magnitude or the smaller the compressibility difference between pile side and pile tip soil layer, the foundation settlement is less sensitive to the change of pile numbers. For low-cap pile group foundation in deep soft soil, pile foundation design based on deformation control can reduce pile numbers considerably, with significant economic benefits.