Abstract: The fact that 70 percent of gypsum mines in our country are underground demands in-depth research on underground mining techniques and damage prevention methods of gypsum mines. On the basis of summarizing already existing research achievements in this field, this paper studied underground mining methods in gypsum mine, analyzed mining techniques and safety managing means in three mining modes. Aimed at pillar-mode that most gypsum mines in our country are in this paper suggested a numerical model to appraise the stability of the upper slab. In this numerical model, Mohr-Coulomb strength criterion was expansively used in tension state, transitional mode of compression and tension was defined, expanded strength criterion could be used both to describe many damage models in rock mass, such as that under compression-shear, tension-shear and tension, and to analyze and appraise stability of upper slab of gypsum mines. Upon that, this paper studied countermeasures to damage caused by geopressure.