Peanut is an economically important oil crop worldwide.A recurrent challenge to peanut industry is the significant loss caused by aflatoxin contamination.Knowledge of molecular mechanisms underlying host resistance could facilitate the genetic improvement of peanut, in order to comprehensively understand the molecular mechanisms of peanut resisting A.flavus, we screened out a NBS-LRR class gene ——AhRAF42 employing peanut high density microarray, which was down-regulated 8 folds by A.flavus under drought stress.Isolating the full length cDNA by the method of rapid amplification of cDNA ends, there were six copies with different lengths of AhRAF42 family.