A simple and rapid method for preparation of plasmid DNA from overnight incubation was introduced. It does not require any additional reagents; the incubation mixture containing recombinant plasmid DNA was just mixed with H₂O and phenol/chloroform/isoamyl alcohol in certain ratio. After vortexing and spinning of the mixture, the supernatant could be directly loaded onto agarose gel and analyzed using electrophoresis. The whole preparation requires only 3～5 minutes. So to quickly screen recombinant clones, this method is better compared with traditional methods.