Abstract Uncontrollable bleeding caused by accidental severe trauma and organ operation severely affects people's life safety, even leading to death. Therefore, it is important to cease the bleeding quickly and effectively. Here, we report a rapid photocrosslinking hydrogel (DP‐F127 hydrogel) based on F127 and acrylate functional motifs for in situ emergency hemostasis. The acrylate groups in DP‐F127 can be cross‐linked within 10 s by UV irradiation. The resulted hydrogels exhibit excellent mechanical properties, biocompatibility, and rapid hemostatic ability. The in vivo studies on the DP‐F127 hydrogel demonstrated that liver bleeding could be rapidly repaired and show significantly less blood loss than commercially available dressing (Gelatin sponge, GS). This study provides a new paradigm for developing a hemostatic hydrogel with the rapid speed of crosslinking for in situ emergency hemostasis.