The present invention relates to a method for preparing a biocompatible small intestinal submucosa hydrogel with a controllable in-vivo degradation period, more particularly to a method for preparing a small intestinal submucosa hydrogel which is formed in a solution phase by forming chemical crosslinkages by solubilizing a biocompatible small intestinal submucosa powder and allows the degradation period of a gel formed during in-vivo injection by controlling the degree of crosslinking and a method for preparing a small intestine submucosa drug carrier or a small intestine submucosa support using the hydrogel.