The three-phase mixed crystal TiO2of anatase, rutile and brookite was prepared by hydrothermal method, and modified with Ag. The crystal structure, morphology and optical property of samples were investigated by XRD, SEM, TEM, PL and DRS. The results show that the prepared TiO2 exhibits a three-phase mixed crystal structure of anatase/rutile/brookite. After Ag modification, the content of rutile increases, and the content of anatase and brookite decrease. Ag element exists in the form of elemental Ag and AgCl. Ag@TiO2 heterostructure is more favorable to the transfer of photoinduced charges and improves the photocatalytic activity. After illumination 90 min, the degradation rate of tetracycline hydrochloride (TC) by Ag modified TiO2 increases from 78.5% to 91.6%.