The Au nanoparticle (AuNPs) and DNA oligonucleotide conjugates will have complicated microstructures because one AuNP can be conjugated to more than one single - stranded DNA (ssDNA) on its surface. In this paper, the AuNPs - DNA conjugates with control lable microstructure were prepared on SiO 2 microsphere carriers. The reactions between AuNPs with ssDNA on SiO 2 carriers were sterically restricted because only out part surface of AuNPs on carriers could react with ssDNA. When two k inds of AuNPs with diff erent diameters, 15 n m and 50 n m, were conjugated with two complementary ssDNA, cleaved from carries and hybridized each other, the AuNPs - DNA conjugates were prepared. The TEM results indicated that when the particle size of AuNPs was about 50 nm, 1 AuNP c ould be conjugated to 2 ssDNA on its surface, while 1 AuNP (15 nm) particle was only conjugated to 1 ssDNA on its surface