Nanoparticles exhibit many interesting properties especially when it is less than 10 nanometer due to its quantum size effect. ZnO nanoparticles have abroad range of electronics, optical, piezoelectric applications due to its direct band gap . In this book it is synthesized in the quantum size by a solvothermal method which is characterized by easy procedure, easy control of particle radius and low coast of processing.Many applications of ZnO nanoparticles could be improved by changing the particle size, morphology and controlling the growth process. This work investigates the effect of temperature, growth period, surfactants and some additives on the particle size, rate constant and energy gap of ZnO nanoparticles. Understanding how these factors enhance or inhabit growth mechanism of ZnO nanoparticles will lead to produce specialized ZnO nanostructures which is important for device fabrication.