The invention relates to a guided tissue regeneration membrane and a preparation method thereof. The method comprises: a pretreatment step, i.e. collecting a mammalian peritoneum, conducting flowing water washing, hair removal and preliminary degreasing for standby use; an antigen removal treatment step, i.e. carrying out further degreasing on the standby peritoneum by means of an enzyme treatment process, an alkali treatment process, an acid treatment process and a hypertonic treatment process, and removing immunogenicity; a collagen fiber contraction treatment step, i.e. carrying out dehydration, non-hydrophilic substance removal and washing treatment on the peritoneum subjected to the antigen removal treatment so as to contract the collagen fibers of the peritoneum; and a drying step, spreading the contracted peritoneum on a culture dish surface to make the compact layer of the peritoneum contact the culture dish, rapidly transferring the peritoneum into a refrigerator at a temperature ranging from -60 to -80DEG C to undergo pre-freezing for 1-8h, then freeze-drying the peritoneums in a freeze dryer for 24-36h, thus obtaining a collagen membrane able to guide tissue regeneration. The guided membrane provided by the invention has a compact layer and a loose layer, also has good biocompatibility, hydrophilicity and bone induction ability, and has a long in-vivo degradation time.