Abstract: Objective To explore the DNA damage in κ-ras gene caused by BaP at the level of nucleic acid.Methods The TK6 cellwas treated with BaP(benzoapyrene),then its genomic DNA was amplified by RDPCR and detected by southern blot with the single-stranded probes of the exon 2 of κ-ras gene.The PCR products were sequenced.Results A clear BaP-induced hybridized band shorter than the exon 2 of κ-ras gene was observed.The sequencing analysis showed that the band was linked by the linker with 67 th base C of the exon 2 of κ-ras.Conclusion It is proved that Bap causes damage in the exon 2 of κ-ras gene,which is located in the 66th base T and maybe be the crucial cancerogenesis target of BaP.