Rapid control of heavy hemorrhaging is critical to save the life of injured individuals.Herein,we developed a novel hemostat employing chitosan-based microspheres,which was prepared by sequential microemulsion of chitosan solution,sol-gel phase transition,and surface modification by 3,4-dihydroxyhydrocinnamic acid(HCA).HCA-modified chitosan microspheres(CSMS-HCA)displayed a porous structure,with a high specific surface area(～211.3 m2/g),accelerating their rapid absorption of blood and concentrating red cells and platelets.The CSMS-HCA exhibited much better in vitro and in vivo hemostatic efficacy than porous chitosan microspheres did.Such a rapid hemostat in the form of microspheres is highly effective in treating deep and irregular wounds,owing to easy accessibility to injured sites.