ZnO layers growth on a-plane sapphire(11-20)substrates by sideflow remote plasma enhanced MOCVD (RPE-MOCVD)was studied. The relation between thickness distribution and growth mode was noticed. We successfully controlled growth from thin layers to nanostructures, by varying growth temperature, pressure and ?/? ratio. The growth temperature dependency of an optical property of the ZnO thin layers was characterized by photoluminescence measurement.