Abstract: This study investigated the effects of three processing methods (direct cooking, cooking followed by ultra-high pressure (UHP) treatment at 300 MPa for 10 min, and UHP treatment prior to cooking) on the quality attributes of grass carp (Ctenopharyngodon idellus) during 4 ℃ storage. The evaluated parameters included total viable count (TVC), total volatile base nitrogen (TVB-N), thiobarbituric acid reactive substances (TBA), shear force, water distribution, and microbial composition. Results demonstrated that UHP treatment significantly (P<0.05) attenuated the storage-induced increases in TVC, TVB-N, and TBA values. Colorimetric analysis revealed UHP treatments induced significant chromatic alterations, manifesting as increased L^* (lightness) and b^* (yellowness) values with decreased a^* (redness). Post-cooking UHP application notably delayed shear force reduction during storage. Low-field NMR analysis identified bound water as the predominant moisture state. Microbial profiling at genus level showed Pseudomonas, Sphingomonas, and Bacillus as dominant spoilage organisms across all treatments. Notably, the cooking-UHP sequence optimally preserved color parameters, textural integrity, and moisture retention, extending shelf life to 18 d versus conventional processing methods. These findings provide technological insights for enhancing the safety and commercial viability of prepared freshwater fish products through optimized UHP processing protocols.