The invention aims to provide a solution for preserving and diluting DNA samples, and belongs to the technical field of polymerase chain reaction (PCR) and the category of dilution and preservation of RNA (DNA) samples. The solution is prepared by the following steps: adding certain amounts of DNA preservative and chemical reagents into deionized purified water; adjusting the pH value to be 7.8-8.2, and enabling the volume to be constant; sealing and conducting autoclaved sterilization for later use at the room temperature. The solution is white and transparent, has the advantages of being stable, easy to preserve, convenient to use and the like, and is suitable for preserving and diluting the DNA samples of serum, plasma, tissue, urine, secreta and the like. When immersed into the solution for diluting and preserving the DNA samples, DNA in fresh tissue cells can be preserved for 1 week at 37 DEG C, 1 month at 25 DEG C, 6 months at 4 DEG C and long term at minus 20 DEG C to minus 80 DEG C in good condition.