On basis of the threedimensional spatial analysis, the article deduces the threedimensional analytic solution for the ultimate bearing capacity of the ground of the rectangular foundations by means of the upper bound principle of the limit analysis method, comprehensively taking into account the influences on the sliding mode and bearing capacity of the ground imposed by such factors as the asymmetric loads, cover depth and overload. The result of the study is applied in an engineering case and comparisons and analysis are made. On basis of the threedimensional analytic solution, the relevant parameters can be obtained by means of simple calculations, thus the ultimate bearing capacity of the ground can be gained. The result of the study can easily be applied in the engineering designs.