As environment-friendly or green cement, the geopolymer cementitious material has high early age strength, good volume stability and durability. In this paper, the mechanical properties of geopolymer hydrates at different hydrating ages were studied by changing the oxide content of raw material. The results showed that the chemical-combined water kept increasing as hydrating age prolonged, and reached the maximum at n(SiO2)/n(Al2O3)=3.9, n(H2O)/n(SiO2)=2.3 and n(Na2O)/n(Al2O3)=0.6. With the development of hydration, the pH value of geopolymer paste showed fluctuated: pH value kept increased at the age of 1d～3d, then decreased at the age of 3d～7d, at the age of 7d～14d the pH value increased again and at last it remained constant at the age of 14d～28d. 28d compressive strength of geopolymer paste reached the maximum as chemical-combined water content was 0.09g～0.10g and pH value was 10～11.