The modified tests are put on by selecting gypsum from different habitats, using doping technology and calcination technology. The tests results can be summarized as follows. Different kinds of gypsums have different effects on the strength of fly ash autoclaved products, and so do the gypsums collected from different habitats. Low-purity gypsums helps to improve the strength of autoclaved products. Low-purity scatter of gypsum can be achieved by means of natural doping and artificial doping, and natural doping is better. Calcined gypsum could increase the strength of fly ash products within a certain range, and the best calcining temperature is about 650°C.