The invention discloses a self-assembling polypeptide and use of the self-assembling polypeptide as a hemostatic agent. The self-assembling polypeptide is RAKA16, or REKD16 or RKDE16, the RAKA16, theREKD16 and the RKDE16 have the characteristics of self-assembly gelation, and solutions of the RAKA16, the REKD16 and the RKDE16 can self-assemble to form hydrogel when the solutions encounter a DMEMmedium or blood. According to the self-assembling polypeptide, the self-gelation characteristics of three kinds of polypeptides are used, a series of novel polypeptide hemostatic agents are prepared,and bleeding stopping of wounds can be effectively conducted.