Abstract: This study aimed to investigate the effects of konjac glucomannan (KGM) with varying molecular weights on the structure and gel properties of myofibrillar protein (MP) derived from frozen Antarctic krill. Using Antarctic krill MP as the research object, we compared the degradation of KGM with molecular weights of 1.5974×10⁶ Da (HMW KGM), 1.2769×10⁶ Da (MMW KGM), and 0.6912×10⁶ Da (LMW KGM) during the freezing storage process at −18 ℃. The effects on structure properties (chemical bond level, carbonyl content, surface hydrophobicity, particle size, myofibril breakage index) and gel properties (water-holding capacity, hardness, elasticity, thermodynamic) were analyzed at 0, 60, 120, and 180 days. Compared to the blank control group (MP without the addition of KGM enzymatic hydrolysis products), the HMW KGM group exhibited the highest holding capacity, hardness, and elasticity after being frozen for 180 days, with values of 67.66%±2.58%, 375.85±6.78 g, and 2.78±0.08 g, respectively. In contrast, the MMW KGM group demonstrated the highest levels of ionic bonds, hydrogen bonds, and disulfide bonds, measuring 27.87±1.03, 20.98±1.12, and 5.19±0.12 mg/g, respectively, while the contents of carbonyl groups and surface hydrophobicity were the lowest. This suggested that MMW KGM was effective in inhibiting the oxidation of MP. Additionally, after 180 days of freezing, the results for particle size, myofibrillary rupture index, and thermodynamic index indicated that the spatial structure of MP in the MMW KGM group was the most stable. These findings confirmed that the addition of MMW KGM provided the most effective freezing protection for the MP of Antarctic krill, which offered theoretical support for the use of enzymatically hydrolyzed KGM as an antifreeze agent during the freezing and storage of aquatic products.