Astragalus polysaccharides (APS) have strong antioxidant effects and may thus be useful for the preservation of semen at low temperaturesin vitro. However, the effects of APS on the quality of frozen-thawed Tibetan boar sperm have yet to be clarified. Here, the effects of APS on the quality and levels of genomic DNA methylation in Tibetan boar spermatozoawere assessed. Tibetan boar semen was cryopreserved in high-density tubules in freezing extender supplemented with 0, 0.2, 0.4, 0.6, or 0.8 g· L-1 APS to determine the optimal concentration of APS. Spermgenomic DNAmethylation levels of the three groups (Fresh grouprepresents freshspermatozoa, No add grouprepresents unsupplemented frozen spermatozoa, and Optimum add group representsfrozen spermatozoa supplemented with the optimal concentration of APS) were detected using a fluorescencemethod. The resultsshowed that spermquality was significantly higher in the group supplemented with 0.4 g· L− 1APS (increased sperm motility, acrosome integrity, and plasma membrane integrity, simultaneously decreased abnormality and the ROS level) than in all other groups. p< 0.05), andthe DNA methylation levels of frozen sperm in this groupwere significantly lower than that of theNo add group (p< 0.05). The results indicated that semen freezing extender supplemented with 0.4 g· L− 1APS was suitable for Tibetan boar semen.