Abstract: Hydration reactions of samples made from skarn-type copper tailings, blast furnace slag, quartz sand, cement clinker and natural gypsum during the process of pre-curing, autoclaving and re-curing were investigated by strength testing, X-ray diffraction analysis and scanning electron microscopy. The influences of calcium and silicon contents on the amount and variety of hydration products generated in the reactions were analyzed and the effects of hydration products on the strength of the samples were discussed. It is found that the strength of autoclaved products in different curing stages depends on the amount and variety of hydration products generated in the curing process, while the amount and variety of them hinge on the amount and existence form of calcium and silicon.