Cystatins are protein inhibitors of cystein proteases belonging to papain family. In plants, cystatins are found to be involved in drought stress. The phytocystatins of plants are members of the cystatin superfamily of proteins. Various biological functions have been attributed for phytocystatins: Physiological functions of regulation of the endogenous proteinases activities in seeds during seeds maturation; Participation of the inhibitors as important element in defence against attack by insects and nematodes that generally contain cysteine proteinases in their guts; and others functions not defined. In this study, the authors present some results on amplification of cystatin gene from DNA isolated from corr cultivar Vietnam (L VN885) via PCR reaction and assessment of drought tolerant ability from some corn cultivars (Zea mays L.) with different level of drought tolerance. This gene is 405 bp in length. The PCR products containing the cystatin fragments were cloned into pBT and sequenced. Comparison of nucleotide sequence of the cystatin gene published on NCBI with the code number D38130 and LVN885 showed a similar degree 99.2 percent. Similar levels of amino acid sequences in proteins cystatin also high (97.7 percent).