The residual stresses and piezoelectric performance of ZnO thin films under different annealing parameters have been studied by X-ray diffraction and atomic force microscopy (AFM). First, ZnO thin films with a thickness of 800 nm were grown on a Pt/Ti/SiO₂/Si substrate by magnetron sputtering. Second, the orthogonal experimental method was selected to study the effects of annealing temperature, annealing time and oxygen content on the residual stresses of the ZnO thin films. The residual stresses of the ZnO thin films were measured by X-ray diffraction and the sin²ψ method. Finally, the three-dimensional topography and piezoelectric performance of the ZnO thin films were measured by AFM. The results showed that the oxygen content during the annealing process has the greatest effect on the residual stress, followed by the annealing temperature and annealing time. A minimum residual stress and optimal piezoelectric performance can be realized by annealing the ZnO thin film in pure oxygen at 723 K for 30 min.