In order to investigate radiosensitized effect induced by WORTMANNIN(WT) the nuclear factor kB (NF-kB) was studied by Electrophoretic  Mobility Shift Assay (EMSA). Double strand nucleotide sequence which contains kB genetic locus was composed, diluted and annealed in pure water, and then labeled as radioactive nucleotide probe. LP3 cell was cultivated in conventional method and receive 5 Gy of γ-irradiation after nurturing with WT. The nucleoprotein picked up from the cell was combined with the radioactive labeled probe and then was carried out with electrophoresis by SDS-PAGE, which was taken photographs using autoradiograph in low temperature after vacuum drying. It has been found that the NF-kB activity of LP3 cell arises from about 8 % to 50 % and then becomes down to 12 % in 6 h after irradiation. WT at 50 µmol/L can inhibit the NF-kB activity evidently. Radiation can activate NF-kB through message pathway and promote the gene express, which is related to repair and other defense mechanism of damaged DNA in cells. WT may block the massage pathway at early stage and induce radiation sensitized effect.