One plasmid DNA with egfp and Kanr was introduced into the natural soil.The positive transformants were isolated directly from the bacterial suspension with flow cytometer and sorted with green fluorescence and kanamycin resistance.The frequency of natural transformation was less than 10-7 in soil.After the enrich cultivation,82 cells out of 39 736 426 were sorted.Positive transformants were finally obtained.The occurrence of horizontal gene transfer through natural transformation in soil was confirmed.Our studies break the lowest proportion limit of sorting with flow cytometry as well.