Objective: In response to the urgent need for ideal dressings for drug-resistant bacterial-infected wounds, this study aimed to develop a multifunctional hydrogel dressing integrating rapid gelation, strong adhesion, controllable self-erosion, fluorescence tracing, and broad-spectrum antibacterial properties. Methods:An ultra-fast in situ forming isoindole?crosslinked hydrogel (OSN) dressing was prepared via a ternary condensation reaction by mixing precursor solutions of o-phthalaldehyde (OPA), tetra-arm poly(ethylene glycol) thiol (tetra-PEG-SH), and tetra-arm poly(ethylene glycol) amine (tetra-PEG-NH?). Three hydrogels (OSN-1, OSN-2, OSN-3) were fabricated by adjusting the molar ratio of OPA to precursors (0.5:1:1, 1:1:1, 2:1:1). The gelation performance, microstructure, mechanical strength, self?erosion behavior, biocompatibility, and antibacterial activity were systematically characterized using scanning electron microscopy (SEM), rheological tests, mechanical analysis, UV/fluorescence spectroscopy, cellular assays (CCK-8, live/dead staining, scratch assay), and antibacterial evaluations (colony counting, SEM, biofilm staining). Results:The OSN hydrogel formed rapidly in situ within 10 seconds, yielding a uniform three?dimensional network. Increasing the OPA ratio accelerated gelation and conferred a self-eroding property, with OSN-3 degrading completely within 24 hours. The hydrogel exhibited excellent tissue adhesion strength (up to 38.8 kPa), favorable biocompatibility, promotion of L929 fibroblast migration, and potent antibacterial activity against both methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli), effectively disrupting bacterial biofilms. Moreover, degradation of the hydrogel was accompanied by the attenuation and eventual disappearance of blue fluorescence due to cleavage of the isoindole rings, enabling real-time fluorescence tracking of the degradation process. Conclusion: This study successfully constructed a multifunctional self-eroding antibacterial OSN hydrogel dressing based on the OPA ternary condensation reaction. The dressing combines injectability, rapid gelation, strong adhesion, controllable degradation, fluorescence tracing, and broad-spectrum antibacterial performance with good biocompatibility, offering a novel and promising solution for developing antibiotic-free intelligent wound management strategies.