High pure ZnO Colloidal nanocrystal clusters ( CNCs) were synthesized by a modified hydrolyzation method. The diameters of as-prepared ZnO crystalline were between 20 and 40 nm, however, the ZnO CNCs arrived at 400-800 nm. The ZnO CNCs sensor were found to have high sensitivity and fast response/recovery time to humidity, and their resistance changed approximately three orders of magnitude from about 1.58 x 10(9) Omega in dry air (10 RH%) to 1.65 x 10(6) Omega in 93 RH% air. Furthermore, the ZnO CNCs sensors were relatively stable to humidity for a long time. (C) 2010 Elsevier B. V. All rights reserved.