Abstract: The whole variation and distribution of effective additional stress acted on the foundation base, tensile stress in reinforced bars in foundation concrete and vertical deformation of the foundation base were investigated via field monitoring. It is found that, the contribution of the effective stress increment of soils overlaid the foundation base to the settlement, which is influenced by dewatering of foundation pit, should not be neglected. Moreover, the compressive stress acted on foundation base can not be simply assumed as evenly distributed load, the resultant largest vertical deformation is not consistent with working point of the largest stress, and the settlement at the centre of foundation maybe not be the largest. Settlement located in different place is not usually uniform, and the largest settlement is only 14.22 mm; the tensile stress of reinforcing bars changed alternately with time, and the maximum tensile stress does not exceed about 22% of the allowable strength of reinforcing bars. Conclusions may offer a reference to the design of the large concrete footing and the layered sandy foundation base.