Abstract: The purpose of the study was to investigate antioxidant constituents in Magnolia offcinalis seed. The 90% ethanol extracts was fractionated by successive extraction with petroleum ether,ethyl acetate,n-butanol and water. The abilities of the extracts and these four fractions on scavenging DPPH,ABTS free radicals and FRAP were measured. Along with this,their total phenolics and total flavonoids contents were determined. The results showed that Magnolia offcinalis seed were rich in total phenolics and total flavonoids. The contents of ethyl acetate fractions were(253.64±7.25) and(179.11±0.61) mg/g,which were the highest in the solvent fractions. Moreover,the ethyl acetate fractions had the strongest antioxidant activity,when compared with enthanol extracts and other three fractions. The IC₅₀of DPPH free radical scavenging activity to ethyl acetate fractions was only(29.33±2.31) μg/mL,which was significantly(P<0.05)higher than the BHT. The ABTS free radical scavenging activity of ethyl acetate fractions was similar to V_C,and the IC₅₀ were(30.33±1.53)and(31.67±3.06) μg/mL,respectively. The ethanol extracts of Magnolia offcinalis seed and fractions,exhibited low FRAP activity,which were lower than V_C and BHT significantly(P<0.05). The correlation analysis showed that these three antioxidant activities were significantly correlated with total phenolics and total flavonoids(P<0.01). The above results indicated that ethyl acetate could enrich the phenolic constituents of Magnolia officinalis seed,which laid a theoretical foundation for the separation of antioxidant constituents in Magnolia officinalis seed.