Abstract: Through a subgrade treatment engineering example, lacustrine soft soil treatment method and settlement rules of Yinchuan city ring road were studied on the basis of the field monitoring. The results showed that the compression coefficient of the lacustrine soft soil is big, its bearing capacity is low, and it has a poor permeability, the soft soil must be treated before the construction of subgrade. Sand-gravel cushion, bag sand well and broken stone compaction pile are some effective methods to treat this lacustrine soft soil subgrade, and design of the subgrade treatment is reasonable and economical, construction procedure is suitable, and the experience from this engineering is valuable for some other similar projects.