Abstract: The compaction performance and compressive strength of materials are important indices need to be considered when selected in foundation treatment. The two factors can be used as quality control parameters in construction and have important they are influence on engineering properties. Lime and slag are both lightweight materials. The rational use of lime-slag mixed materials in foundation treatment can achieve the results of reducing the additional stress in foundation, and it is an economic and environmentally friendly way because vast industrial waste can be used. The strength increasing mechanism of lime-slag mixed materials is theoretically analyzed. Compaction tests and unconfined compressive strength tests are on the lime-slag mixed materials with different mix proportions by volume are carried out. The compaction property and unconfined compressive strength are obtained. Combined with an engineering example, a foundation treatment project using piles of lime-slag mixed lightweight materials is analyzed and calculated, indicating that this kind of mixed materials can be used in foundation treatment.