Based on the Rapid-Transit Tram Project in Nanjing, three soft soil improvement methods including replacement method, vacuum preloading method, as well as vacuum preloading combined with cement-soil mixing pile method were introduced in this paper.. The reinforcement method and the construction technology were reported in detail for the three methods. The post-construction settlement of the soft soil foundation reinforced by the three methods was investigated. It can be found that the post-construction settlements were 15.8 mm, 13.2 mm and 8.6 mm for replacement method, vacuum preloading method, and vacuum preloading combined with cement-soil mixing pile method respectively, which were much less than the cumulative alarm value of 100 mm. It can be concluded that these three improvement methods reinforced the soft soil foundation effectively, whereas the reinforcement effect of the vacuum preloading combined with cement-soil mixing pile method is better than the other two methods.