4-methyl-7-hydroxycoumarin was prepared by the acid-catalytic reaction of the resorcinol with ethyl acetoacetate and then 4-methyl-7-acetoxylcoumarin was obtained by the esterification of 4-methyl-7-hydroxycoumarin. The structure of the compound was confirmed by melting point, nuclear magnetic resonance hydrogen spectroscopy (1H NMR), nuclear magnetic resonance carbon spectroscopy(13C NMR) spectrum, and ultra high performance liquid chromatograph electrospray ion source mass spectrometer(UHPLC-ESI-MS). Antioxidant abilities of the obtained compounds were evaluated by inhibiting 2,2’-azobis(2-amidinopropanehydrochloride) (AAPH)-, Cu2 /glutathione (GSH)-, and ?OH- induced oxidation of DNA. The radical-scavenging properties of the obtained compounds were estimated by quenching 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS ?), 2,2’-diphenyl-1-picrylhydrazyl (DPPH), and galvinoxyl radicals, and then the structure-activity relationship of these compounds could be explored. The results showed: (1) 4-methyl-7-hydroxylcoumarin not only exhibited the ability to protect DNA against AAPH, Cu2 /GSH and ?OH-induced oxidation, but also scavenged ABTS ?, DPPH, and galvinoxyl radical, respectively; (2) 4-methyl-7-acetoxylcoumarin can only inhibit the DNA oxidation reaction by ?OH and Cu2 /GSH, and scavenge ABTS ? and DPPH radicals; (3) 4-methyl-7-acetoxylcoumarin had antioxidant property, while antioxidant property was reduced when hydroxyl was protected, revealing that 4-methyl-7-hydroxylcoumarin has strong radical-scavenging properties and reduction ability , can be a potential antioxidant.