The phlogopite-vermiculite interstratification mineral samples from the Weli mine of Xinjiang were acidized with hydrochloric acid. Based on an analysis of chemical composition and XRD of the samples, the authors studied chemical composition and contents of the acid soak-out substances as well as the structure characteristics of the samples treated with hydrochloric acid. The acid corrosion mechanism and the content variation tendency of the soak-out substances with the increase of hydrochloric acid concentration were also investigated. The results show that the acid soak-out ratios of CaO and Na2O are the highest, followed by K2O. The acid soak-out ratios of MgO, Fe2O3 and Al2O3 are relatively high, while the acid soak-out ratios of SiO2 are the lowest. The acid corrosion amounts of the samples with more vermiculite layers are relatively high. The acid-resistant property of the phlogopite-vermiculite interstratification mineral is not so good as phlogopite.