The growth kinetics of quantum dots (QDs) is of great importance to control and understand their particle size evolution. Water content is an important parameter for the growth of ZnO QDs during the sol-gel process, which has not been precisely studied until now. Herein, a modified sol-gel method was proposed to prepare uniform and mono-dispersed ZnO QDs. In this method, water content was precisely controlled, which facilitated the thorough investigation concerning the effects of water content on growth kinetics of ZnO QDs. When the water content was low (<= 90 mM), the precursor solution was stable and the generation of ZnO QDs could not be triggered. When the water content was too high (3 M), Zn-HDS was generated instead of ZnO. When the water content was in an appropriate range (360 mM-900 mM), the growth of ZnO QDs followed two stages: the oriented attachment (OA) and the Ostwald ripening (OR) stage. Based on our particle size calculation results by Sarma Model, which showed more distinct differentiation and better pertinence than EMA Model, it has been proved that the increase in the water content could not only promote the growth rate of OA stage, but also the OR stage. This results changed our previous thinking that water content has no influence to the OR stage.