The higher LET, the more effeciently strand break occured. All of the natural compound used in this study has ability to protect against DNA damage either in low and hight LET with different capacity. Most of all results incicate that the yield of the SSB from decrease as the concentration of radical scavengers increased. By comparing either in low and high molecular damage EGCG and AA acted as strong scavengers and the stronger is EGCG.