Maysin, a C-glycosylflavone, was isolated from the silks of maize, Zea mays L. The ESI mass spectrum indicates that molecular weight of maysin is $577 extrm{M}^+$m/z, and the ether-linked sugar is rhamnose, $431 extrm{M}^+$m/z (MW$^{+}$-146). The DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging activity of maysin was higher than that of rutin. However, as compared with its aglycon luteolin, maysin showed the relatively moderate DPPH scavenging activity mainly due to the glycosylation of two sugars moieties, keto-fucose and rhamnose. In the in vitro cytotoxicity test against the five human tumor cell lines such as lung (A549), ovarian (SK-OV-3), melanoma (SK-MEL-2), central nerve system (XF-489), and colon (HCT-15), maysin exhibited the relatively weaker activities than cisplatin. The $ extrm{ED}_{50}$ values of maysin were 62.24, 43.18, 16.83, 37.22, and 32.09/$mell$, respectively. Result suggests that maysin is a potential cytotoxicity compound, particularly for human colon, central nerve system, and melanoma tumors.s.