Several conventional methods for preparing gold nanoparticles and their features are reviewed,Which are separated into physical metnods. The physical methods include vacuum evaporation,soft landing and laser ablation, and chemical methods the chemical ones have colloidal metheds,crystal species generating metheds,reverse micellar methods,phase transmission and model methods,etc..Gold nanoparticles with different size and shape can be produced by different methods. Peculiar physical and chemical properties of gold nanoparticles make them have wide applications in fields of chemistry, biology and medicine, especially in DNA detection. There are optical, electrochemical and piezoelectric methods for detection of DNA. The sensitivity and detection range of these methods can be significantly improved with the using of gold nanoparticles.