ZnO thin films on (001) $Al_2O_3$ substrates have been deposited by pulsed laser deposition(PLD) technique using an Nd:YAG laser with a wavelength of 266 nm. The influence of the deposition parameters, such as oxygen gas flow, substrate temperature and laser energy density variation on the properties of the grown film, was studied. The experiments were performed for substrate temperatures in the range of $300~450^{circ}C$ and oxygen gas flow rate of $100~900$ sccm. We investigated the structural and optical properties of ZnO thin films using X-ray diffraction(XRD) and photoluminescence(PL).