Abstract: The unconfined compression shearing tests, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) methods are used to clarify the strength behavior and microstructural evolution of cement-stabilized soils with geopolymer (metakaolin), and then the in-situ tests are conducted to verify their practicability and economy. The results show that when the geopolymer MK is incorporated into the cement, the strength of cement-stabilized soils is obviously multiplied, and significantly better than that modified just by the pure cement, which means that the strength behavior of cemented soils can be further improved. It should be noted that the strength of cement-stabilized soils does not linearly increase with the mixing ratio of geopolymer; its growth efficiency can be divided into the active and inert zones; and the threshold mixing ratio of MK is 3% in this case. The microstructural analysis shows that the MK incorporation can produce more cementation and make the sample denser. Furthermore, the proposed strength enhancement prediction model also verifies these findings. Finally, the analysis of the in-situ strength and economy also shows its effectiveness and the potential engineering application.