Abstract: A consolidation model under the vacuum condition is presented. Two different computing schemes of one dimensional consolidation may be developed according to this model. It is shown that these two schemes come to the same results. The above-mentioned concept can be extended to two- or three-dimensional and axisym-metric problems.The variation of effective stresses in a consolidating soil under negative pressure then can be obtained and theoretically explained by a computer analysis for different boundary conditions. These theoretical findings are confirmed by laboratory and field test. Furthermore, the effects of vacuum preconsolidation for different kinds of soil are demonstrated, and measures of how to improve it are suggested.