In order to investigate the charge transfer protection mechanism on DNA and its electrophilic nucleotide-dTMP, caffeic acid (DHPAA) and methyl caffeate (MDHPA)protectors have been studied in detail. DHPAA and MDHPA belong to phenylsubstituted unsaturated carboxylic acid, thus, their E A may be as high as maleic or fumaric acid and their energies of lowest empty molecular orbitals are 1.79eV、1.75eV respectively and lower than that of thymine (2.60eV) and cystine (2.02eV). Besides, caffeic acid and bases of nucleotides form long chain of stacked arrays which is beneficial for long range electron transfer from pyrimidine anion to electrophilic acceptor-DHPAA or MDHPA. These predictions are strongly confirmed by ESR studies. The ESR spectra from dTMP-DHPAA (,g,=2.0041, H,pp,=15.38,G,) and dTMP-MDHPA (,g,=2.0043, H,pp,=14.33,G,) with minor molar radio of DHPAA or MDHPA to dTMP 1:10, irradiated and recorded at 77K, reveal characteristic similar to that from DHPAA (,g,=2.0042, H,pp,=13.72,G,) or MDHPA(,g,=2.0043, H,pp,=13.44,G,), which represent carboxylic anion radical ,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489723&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489717&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489716&type=, alone, and different from dTMP (,g,=2.0040, H,pp,=24.45,G,). After annealing at room temperature the ESR patterns changed into that from DHPAA or MDHPA alone at room temperature and no traces of ESR signal from 5-thymyl radical could be found. Regarding the binary systems of DNA-DHPAA. DNA-MDHPA with minor molar ratio of protector to nucleotide (1:4), ESR spectra from DNA-DHPAA (,g,=2.0034, H,pp,=18.72,G,)、DNA-MDHPA (,g,=2.0034, H,pp,=19.40,G,) also reveal the characterisitic similar to that from DHPAA or MDHPA alone, irradiated and recorded at 77K. After annealing at room temperature these ESR patterns also changed into that from DHPAA or MDHPA alone at room temperature and no traces of the well known octet pattern from 5-thymyl radical coulal be found.