Pure ZnO and Zn0.96Na0.04O films were grown on quartz substrates by sol-gel technology.The XRD analysis revealed that all thin films had hexagonal wurtzite structure and obvious c-axis preferred orientation.Ferromagnetism was precisely measured by an alternating gradient magnetometer (AGM).To explore the nature original ferromagnetism,the effect of annealing atmosphere on magnetic properties of the films was studied.Compared with pure ZnO,magnetic hysteresis loops showed that doping Na atoms enhanced saturation magnetism.The magnetism of the films annealed in the air atmosphere was significantly better than that in the O2 atmosphere.The photoluminescence (PL) spectrum analysis suggested that the ferromagnetism was due to the defects in the films.