The unconfined compression strength(UCS) test, X ray diffraction(XRD) and scanning electron microscope(SEM) were used to investigate the stabilization effect of geopolymer on clay. The effect of activator modulus ratio and content on the strength development of geopolymer stabilized clay was studied and its micromechanism was analyzed. The results show that geopolymer stabilized clay has a rapid strength gain during curing. The highest value of UCS of 437MPa is observed at activator modulus ratio is 12. The addition of activator content increases the short term strength of geopolymer stabilized clay but has a lower impact on the 14d and 28d strength. When activator content exceeds 50%, strength incensement effect is much lower. Furthermore, N A S H gel, C S H gel, calcium carbonate crystal and mullite crystal are observed in geopolymer stabilized clay. The pores are filled well and the clay is enhanced by geopolymer. Finally, the proposed strength enhancement prediction model is established based on the test results.