Abstract: By the means of analyzing of soft treatment effect of vacuum preloading in the project of jiaojiang polluted water-treatment factory, the authors state that:1 contrast to the preloading,the theory of vacuum is different and it is more effective to the soft soil in the depth. 2 the effect of vacuum preloading is influenced not only by the vacuum stress, but also the number of vacuum pumps, also named unit area vacuum power 3 It is also analyzed that the calculation of settlement, the vacuum stress declining and consolidation delay with depth.