The invention discloses a method for preparing a
collagen sponge under an acid condition. The method comprises the following steps: mixing a corium layer of
mammal skin, quicklime and water, and conducting oscillating at
room temperature; conducting eluting by virtue of an eluent; conducting freeze-
drying and crushing the freeze-dried material into particles; mixing the particles with an
acetic acid solution containing pepsase, conducting stirring and centrifuging, and taking the supernatant; conducting
salting out so as to precipitate collagen and purifying the collagen; and then, dissolving the collagen in an
acetic acid solution, regulating pH to 1-5, injecting the obtained material into a mould, conducting freeze-
drying and cross-linking treatment, and conducting packaging and sterilizing, so that the finished
collagen sponge product is obtained. According to the preparation method provided by the invention, a high-purity
raw material can be directly extracted by virtue of a two-
step method, and in a process of preparing the
collagen sponge, rather than a rigid requirement on
neutral pH of a collagen solution, the ideal collagen
sponge is prepared under a low-pH condition, so that a production process is effectively simplified and preparation cost is reduced.