Objective To compare the effects of four pretreatment methods-hot pressing (HP), steam explosion (SE), ultrasound (US), and solid-state fermentation (SF)-on the structural characteristics and antioxidant activities of Polygonatum sibiricum polysaccharides (PSP), and to explore the potential application of PSP in fruit preservation.Methods Ten PSP samples are prepared. The yield, relative molecular mass, functional groups, thermal stability, surface morphology, and DPPH·, ABTS·, and OH· free radical scavenging abilities of the samples are determined. The PSP sample with low relative molecular mass obtained by SE treatment is loaded with Zn²⁺ to prepare a sprayable hydrogel, which is then applied in the preservation of 'Shatangju' mandarins.Results The yields of PSP from SE and US treatments are the highest (~10%), and are higher than those from HP and SF treatments (P<0.05). The PSP samples from SE and US treatments have low relative molecular mass (32.92×10³ to 49.15×10³), which is significantly lower than that of samples from HP and SF treatments. All the ten samples show similar functional groups and thermal stability, while they differ in surface morphology. In the concentration range of 0.5 to 4.0 mg/mL, all the samples exhibit concentration-dependent scavenging rates against DPPH·, ABTS·, and OH· free radicals. The antioxidant activity of PSP from SE treatment is higher than that from the other treatments (P<0.05). The Zn²⁺-loaded sprayable hydrogel prepared from SE-derived PSP with low relative molecular mass effectively reduces the weight loss rate of 'Shatangju' mandarins during storage, slows down the decline in fruit firmness and the progression of mildew, and exhibits good antifungal effects, with Zn²⁺ being the key component responsible for the antifungal activity.Conclusion SE treatment offers significant advantages in obtaining PSP with low relative molecular mass, improving the yield and antioxidant activity, and showing application potential in fruit preservation.