The more effectively and more rapidly method was used to purify ctDNA of wheat in this paper.The high ionic strength and ascorbic acid were used to get higher yield and better purity.A clearly restriction enzyme mapping would be obtained.High ionic strenth would decrease the electrostatic interaction

and decrease sticking loss that was led by electrostatic interaction between the DNA and protein.Ascorbic acid would provide a low pH condition to restrain the activity of enzyme.