Abstract: <FONT face=Verdana>With ZnSO4?7H2O and NaHCO3 as principal raw materials,nano-sized ZnO was prepared by solid state reaction at room temperature combining with microwave pyrolysis.In order to improve surface physical-and-chemical properties of nano-particles of ZnO,stearic acid was adopted to modify ZnO surface.Modification process conditions,modification mechanism,and influencing factors of nano-sized ZnO particle′s lipophilic properties were discussed.Modified nano-sized ZnO was characterized by FT-IR.Results showed stearic acid and nano-sized ZnO were linked by covalent bonds,and dispersibility of nano-sized ZnO in organic solvent were much better after modification.Optimal conditions of surface modifying were as follows:mass fraction of stearic acid was 10%,modification temperature was 60 ℃,and modification time was 40 min.</FONT>