Abstract: The technique for introducing exogenous DNA into plants, based on DNA fragments crossing hypothesis, is used to directly introduce total DNA or target gene into plants, so as to produce a large quantity of variant materials for variety improvement by means of screening. As it is simple and not subject to restriction of species of plants, more and more breeders accepted and used the technique in rice, wheat, cotton, soybean, maize and vegetables, have bred new cultivars with disease resistance, pest resistance or other good characteristics. Foundation of the technique gave an impetus to plant molecular breeding research.