The immediate control of a hemorrhage is crucial for reducing fatalities in critical situations such as battlefields, traffic accidents, natural disasters, etc. Most existing commercial hemostatic powders have weak adhesion capability and poor biodegradability, restricting their clinical use. In this paper, a new poly(ethylene glycol)-di(cyanoacrylate) (CA-PEG-CA)-based hemostatic powder with tissue-contact-triggered strong adhesion and controlled fast degradation is proposed. The monomers quickly underwent crosslinking polymerization while in contact with tissue or blood, forming an in situ gel on the wound. The hemostatic mechanism was demonstrated to depend on both adhesive-based sealing and the aggregation of platelets and erythrocytes. The powder showed excellent hemostatic effects both in vitro and in vivo, even in a rat model with a weakened native hemostatic capacity. In addition, the poly-CA-PEG-CA gel could be rapidly biodegraded by ester bond hydrolysis. Notably, a cysteamine (CS)-containing solution could accelerate the degradation rate, endowing the gel with an on-demand removal property. This hemostatic powder not only can be used to efficiently control bleeding in emergency scenarios, but it can also allow nontraumatic re-exposure of wounds during subsequent surgical care. These properties make the CA-PEG-CA powder a promising candidate to act as a multifunctional wound care agent for first aid.