Abstract: The solidified bodies are prepared by adding different content jarosite slag in Portland cement by normal curing at 50 ℃, 100 % humidity and for 56 d. The effects of addition amount of jarosite slag on strength and microstructure of solidification body are studied. The effects of the hydrothermal extreme environments with temperature of 200 ℃and pressure of 1.56 MPa on the structure, morphology and strength of solidified body are studied. The result indicates that after being cured at normal condition, the phase of solidifies body are trabzonite, hydration calcium aluminum silicate and hydration calcium. The structure of solidification body becomes loose, and the content of gypsum increases with the increase of jarosite slag content. After being treated in extreme environments, the phase of solidifies body are mainly calcium aluminum silicate and calcium silicate with increase of crystallization, dehydrating of gypsum, loosening of solidification structure and reduction in its strength, and the maximum addition amount of jarosite is 60 %.