We investigated the antioxidant effect of Taraxacum mongolicum glycoprotein (TMGP) in vitro and in vivo.The reaction system of H₂O₂,Fe²⁺,DPPH· and total antioxidant capacity was used to detect the antioxidant activity of TMGP in vitro and was compared with V_C.The contents of MDA and the activities of SOD,CAT,GSH-Px in plasma,liver and brain were respectively measured in aged mice model induced by D-galactose.The result showed that:(1)The scavenging capacity of TMGP for H₂O₂ and Fe²⁺ were enhanced as TMGP concentration increased.The H₂O₂,Fe²⁺ scavenging rates reached 76.8% and 55% respectively at 1.72 mg/mL TMGP,close to the level of V_C;When TMGP concentration at 1.5 mg/mL,the DPPH· scavenging rate reached 77% and it was near V_C;(2)The animal experiment showed that the content of MDA decreased and the SOD，CAT，GSH-Px activities increased in plasma,liver and brain in all TMGP groups,significantly increased the antioxidant capacity of mice.TMGP has obvious antioxidant effect in vitro and in vivo.