Abstract: ZnO nanoparticle and ZnO-Cr2O3,ZnO-Cr2O3-NiO,ZnO-Cr2O3-NiO-MnO doted nanoparticles were synthesised.In the systems of OP/heptane/1-hexanol/H2O reversed microemulsion,the effects of precursor,reactant concentrations and subsequent treatments on preparation and size of nanoparticles were studied.The results show that OP/heptane/1-hexanol/H2O reversed microemulsion systems is suit for preparation of ZnO and its doted nanoparticles,and size of nanoparticles can be controlled by choose of precursor and different reactant concentrations.These ultrafine ZnO nanoparticals have size ranging from 10-200?nm and the doted ones have size of 20nm.